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Towards Healthy Levels of Carbon Dioxide in Schools of the National Oil Company of Abu Dhabi

Towards Healthy Levels of Carbon Dioxide in Schools of the National Oil Company of Abu Dhabi Hindawi Advances in Meteorology Volume 2021, Article ID 6680476, 11 pages https://doi.org/10.1155/2021/6680476 Research Article Towards Healthy Levels of Carbon Dioxide in Schools of the National Oil Company of Abu Dhabi 1 1 2 1 AliAbu-Rahmah , RasheedAhmad, AbdelmaoulaHaboub, andYasminAbu-Rahmah ADNOC Schools, Abu Dhabi, UAE Nikon Research Corporation of America, 1399 Shore Way Road, Belmont 94002-4107, CA, USA Correspondence should be addressed to Ali Abu-Rahmah; aliaburahmah@yahoo.com Received 22 December 2020; Revised 17 April 2021; Accepted 14 July 2021; Published 22 July 2021 Academic Editor: Antonio Donateo Copyright © 2021 Ali Abu-Rahmah et al. %is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In their annual indoor air quality assessment for ADNOC Schools, the Abu Dhabi Education Council has reported hazardous levels (∼3000 ppm) of carbon dioxide in fifteen classrooms. Exposure of 5,090 students attending the school for ∼eight hours (typical school day) to such high levels of carbon dioxide would induce adverse health conditions like headaches, drowsiness, and lack of concentration on the short term and serious diseases like asthma and sick building syndrome on the long term. %e Health, Safety, and Environment committee of the school has identified clogged air intake vents and dirty AC filters as the main cause of the high carbon dioxide concentrations reported. %e outdoor (ambient) carbon dioxide level is measured and has an eight-hour average value of 419 ppm. After cleaning thoroughly, the indoor levels of carbon dioxide, temperature, and relative humidity were monitored simultaneously in each classroom and have average values of∼1117 ppm,∼24 C, and∼37%, respectively. In addition, the average indoor-to-outdoor ratio of carbon dioxide has been improved from 3000/419 ≈ 7.2 before cleaning the AC filters to an average ratio of (1, 117/419 ≈ 2.7) after cleaning. %us, ventilation rates in the classrooms monitored in this project are adequate and the corrective actions taken were effective. In particular, children are more sensitive to pollutants than 1. Introduction adults because they have high inhalation rates per body mass Data of the US Environmental Protection Agency (EPA) and their respiratory and immune systems are still devel- indicate that indoor pollution levels may be 2–5 times higher oping [4]. Failure to respond promptly to IAQ problems in than those of outdoor levels [1]. High levels of indoor air schools may lead to short- and long-term respiratory health pollution are of particular interest because it is estimated issues [5] as dry cough, rhinitis, and nasal patency in that people spend most (∼90%) of their times indoors [2]. children [6]; occurrence of sick building syndrome among %e exposure to high levels of indoor air pollutants has students [7, 8]; asthma [9]; and poor academic achievement increased over the past several decades. %is increase may be [10]. attributed to reduction of ventilation rates to save energy; %e adequacy of the supply of fresh air in buildings use of synthetic building materials and furnishings; and use including schools is commonly evaluated by investigating of chemically formulated personal products, pesticides, and the level of carbon dioxide (CO ) concentration in a room cleaning supplies. [11, 12]. %is gas is a natural constituent of the atmosphere In schools, good indoor air quality (IAQ) contributes to and is emitted from humans during exhalation. High a favourable learning environment for students, protects concentration levels of CO indicate poor air quality due to health, and assists with the core mission―education. %e inadequate ventilation. %is may cause students to loss presence of a wide variety of emission sources like art and conscious (fainting), to get headaches, or to function with science supplies makes sustaining good IAQ a challenge [3]. lower activity levels. %e relation between CO 2 2 Advances in Meteorology concentration and student absences was investigated [8, 13]. In ADNOC Schools, a mechanical (SKM, model APCN- %e relation between certain CO concentration levels and 5240Y) HVAC system has been placed on the rooftop. %is the corresponding IAQ effects is summarized by Pietrucha system incorporates bag and metal filters to extract dust [14] in Table 1. from air flowing to the buildings. %e manufacturer rec- ommends a quarterly cleaning for most air filters. However, %e concentration of CO gas in a given sample of air is the UAE has a dusty environment, which demands a more relatively easy to measure [15]. Its concentration is expressed frequent cleaning of AC filters. in units of parts per million (ppm); a ratio that indicates the In resolving the high CO levels reported by the ADEC, number of CO molecules per million molecules of air. 2 2 clogged filters have been cleaned thoroughly and defective Outdoor CO levels must be measured when assessing in- bag filters are replaced. Windows’ rubber frames have been door concentrations because the outdoor CO directly maintained. Figure 1 shows a random AC filter before and impacts the indoor concentration. In outdoor air, CO after cleaning. concentration normally varies from 350 to 450 ppm [16]. Effectiveness of the corrective actions taken in this %e adequacy of ventilation may be measured by the number project has been evaluated by monitoring the CO con- of cubic feet of air per minute (cfm) provided per person. 2 centration levels before and after cleaning the clogged AC Alternatively, adequacy of ventilation can be evaluated by filters. Ten-minute walk-through measurements were taken indoor CO concentrations. For instance, a CO level of 2 2 before and after cleaning the filters. Measurements were 1000 ppm is equivalent to 15 cubic feet of fresh air per made using the portable Fluke model 975 air meter, which minute per person [17]. %e American Society of Heating, monitors CO concentration levels, temperature, and rela- Refrigerating, and Air Conditioning Engineers (ASHRAE) tive humidity simultaneously. %e range, resolution, and has recommended indoor CO levels that do not exceed the accuracy of this instrument are summarized in Table 2 local outdoor concentration by more than about 700 ppm below. [18]. %e ASHRAE standard 62.1–2013 recommends indoor Since the indoor CO concentrations are directly im- CO levels at less than 1000 ppm in schools and 800 ppm in 2 pacted by the outdoor CO levels, the ASHRAE recom- offices [19]. %e National Institute for Occupational Safety mends an indoor CO standard maximum level that does and Health (NIOSH) considers that indoor air concentra- 2 not exceed the outdoor concentration by more than about tions of CO that exceed 1000 ppm are a marker of inad- 700 ppm [23]. %us, another identical air meter was placed equate ventilation [20]. Indoor air temperature (T) and on the rooftop near the inlet of the AC ventilation to relative humidity (RH) are key indicators of occupants’ quantify the background CO levels. Care was taken to place thermal comfort [21]. High RH may cause condensation and air meters in locations that would not be directly impacted mould formation, which is unhealthy for occupants and by the breath of individual children. In each location, the children [22]. meter was placed one meter above the floor at the level of In their annual IAQ walk-through assessment of student desk and about one meter from the walls, away from ADNOC Schools, the Abu Dhabi Education Council doors and windows, thus avoiding possible air disturbances (ADEC) has reported hazardous levels (∼3000 ppm) of CO . as can be noticed in Figure 2. Such high levels of CO would induce adverse health To reach a steady state of occupancy and ventilation, conditions like asthma, headaches, drowsiness, and lack of doors and windows of each classroom are kept locked and a concentration to a large number of personnel (∼6304) reasonable time (∼5 minutes) was allowed before each distributed among 6 campuses of ADNOC Schools. In measurement could be made. Ten-minute measurements particular, 5090 students spending ∼8 hours of their time could be made during lessons (occupied periods). %e code indoors would be affected mostly as their respiratory system number of each classroom is stored in the memory of the air is still developing. %erefore, the Health, Safety, and Envi- meter ahead of measurements. Following this methodology, ronment (HSE) committee of the school has decided to a real-time monitoring of CO levels, temperature, and RH is reduce the reported high CO concentration levels. %e aim 2 made in fifteen locations indoors of the male campus of this study is to evaluate the indoor air quality before and building of ADNOC Schools before and after cleaning of the after a set of corrective actions were taken. AC filters. 2. Methodology 3. Results and Discussion %e environment inside a building can be controlled by a Air quality was evaluated during the typical school day of th system of heating, ventilation, and air-conditioning January 8 2015. Indoor CO concentrations are directly (HVAC). %is system maintains a comfortable humidity impacted by the outdoor (background) CO levels. %us, the level and uses a thermostat to control the air temperature indoor and outdoor CO levels, air temperature (T), and RH inside a room by heating or cooling. %e HVAC system were measured simultaneously. dilutes indoor pollutants with outdoor air. Fans circulate air through filters to extract dust. To supply clean air, an inlet is placed (on roof ) as far as possible from the ground. 3.1. Outdoor Air Quality. %e outside air concentration of However, leaky windows allow dust to clog filters, which CO is measured close to the region where the fresh air is slows air circulation and causes buildup of high CO levels. drawn into the building. An air meter was placed on the 2 Advances in Meteorology 3 Table 1: Description of indoor air quality on the basis of CO concentrations. Indoor CO Description of indoor air quality 350–400 ppm Normal background concentration in outdoor ambient air 400–1,000 ppm Concentrations typical of occupied indoor spaces with good air exchange 1,000–2,000 ppm Complaints of drowsiness and poor air Headaches, sleepiness, and stagnant, stale, stuffy air. Poor concentration, loss of attention, increased heart rate, and 2,000–5,000 ppm slight nausea may also be present 5,000 ppm Workplace exposure limit (as 8-hour TWA) in most jurisdictions >40,000 Exposure may lead to serious oxygen deprivation, resulting in permanent brain damage, coma, even death Precleaning Postcleaning Figure 1: Typical HVAC filter precleaning and postcleaning in ADNOC Schools. Table 2: Accuracy, resolution, and range of Fluke 975 air meter. Measured parameter Range Display resolution Accuracy % of reading CO 0 to 5000 ppm 1 ppm 2.75% + 75 ppm ° ° ° ° ° ° Temperature −20 to 50 C 0.1 C ±0.5 C from 5 C to 40 C Relative humidity 10 to 90% RH 0.1% ±3% RH from 10 to 90% RH background CO levels as referenced to the primary axis of Figure 3, while the ambient temperature in degree Celsius and RH are both measured and referenced to the secondary axis. Outdoor CO concentrations varied from 404 ppm at 9 : 45 am to 435 ppm at 7 : 31 pm with an eight-hour average value of 419 ppm. %is background CO is normal and primarily due to vehicle emissions. Outdoor air temperature ° ° has varied from 21 C at 7 : 11 am to 28 C at 2 : 19 pm with an Air meter Particle counter average of ∼26 C, while the RH has varied from 40% at 2 : (Fluke 975) (Fluke 985) 21 pm to 77% at 7 : 11 am with an average of ∼57%. Bus loading/unloading areas, staff parking lot, swimming pools, and shaded playground shown in Figure 4 are identified Figure 2: Air-quality monitors used in this study. as hazardous zones (for students/staff who are in these areas) during the time intervals 7 : 10–8:00 am and 2 : 30–3:00 pm. central area of the rooftop near the inlet of the AC units. %e %ese zones are all outdoor locations. During bus loading and outdoor air quality has been measured continuously as a unloading times, students and staff who are close to buses are function of Abu Dhabi local time from 7 : 00 am to 3 : 00 pm advised to wear a face mask as they are exposed directly to CO with two-minute intervals. %is measurement monitored the levels that are much higher than those detected on the rooftop. 4 Advances in Meteorology 440 80 420 50 400 20 Abu Dhabi local time Ambient (outdoor) CO Outdoor temperature (C) Outdoor CO average (419 ppm) Relative humidity (%) Figure 3: Outdoor levels of CO , relative humidity, and temperature. Bus loading zones Parking lot Shaded yard Science labs Figure 4: Hazardous zones around the campus of ADNOC Schools. 3.2.IndoorAirQuality. To assess the impact of cleaning AC their average values are represented in the bar graphs of filters on indoor air quality, the indoor CO levels were Figures 6–8. measured before and after cleaning the clogged AC filters in Figure 5 shows data sets of CO levels, air temperature, fifteen locations within the main campus of ADNOC and RH simultaneous measurements in fifteen indoor lo- Schools. %e locations selected include ten classrooms, four cations (Classrooms, Labs) after the cleaning of the AC labs, and one cafeteria. Cafeteria and labs are included as filters. Each graph can be identified with the name and code they represent spaces with different occupancy, area, and of the class/lab. %e indoor CO curves are referenced to the activity levels. Ten-minute walk-through CO , temperature, primary axis, while the indoor air temperature and RH and RH measurements with one-minute increment have curves are referenced to the secondary axis (to the left of each been made; their averages are summarized in Table 3. %e graph). %e graphs are arranged in the same sequence during results are represented by time-series graphs in Figure 5, and the time that data have been collected. Ambient CO levels (ppm) 6:28 AM 6:43 AM 6:57 AM 7:12 AM 7:26 AM 7:40 AM 7:55 AM 8:09 AM 8:24 AM 8:38 AM 8:52 AM 9:07 AM 9:21 AM 9:36 AM 9:50 AM 10:04 AM 10:19 AM 10:33 AM 10:48 AM 11:02 AM 11:16 AM 11:31 AM 11:45 AM 12:00 PM 12:14 PM 12:28 PM 12:43 PM 12:57 PM 1:12 PM 1:26 PM 1:40 PM 1:55 PM 2:09 PM 2:24 PM 2:38 PM 2:52 PM RH (%) and temperature (°C) Advances in Meteorology 5 Table 3: Indoor air-quality parameters precleaning and postcleaning the AC filters. Precleaning AC filters Postcleaning AC filters Vol. No. of Grade CO CO CO 2 2 2 Location Code 3 T RH CO levels T RH (m ) occupants level levels indoor/ indoor/ ° ° ( C) (%) (ppm) ( C) (%) (ppm) outdoor outdoor Arabic classroom G138 238 12 9 2,893 27 63 6.90 1,048 25 38 2.50 Arabic classroom G132 238 17 7 3,098 26 67 7.40 1,318 24 42 3.15 Math classroom G009 253 7 12 2,897 25 63 6.91 1,189 24 37 2.84 English G008 156 8 12 3, 311 25 64 7.90 1,308 24 38 3.12 classroom Chemistry lab G123 140 10 10 2,792 24 69 6.66 1,033 23 43 2.47 Cafeteria G106 756 44 6–12 3,381 25 66 8.00 1,087 24 41 2.60 Physics lab G083 349 13 12 2,778 25 65 6.63 971 24 39 2.32 Hum. classroom G074 196 10 8 3,009 24 65 7.18 1,272 23 41 3.00 Hum. classroom G075 196 13 8 2,625 25 62 6.26 1,330 24 34 3.17 Arabic classroom G134 238 17 7 3,117 25 61 7.44 1,286 24 32 3.07 Art lab G087 349 21 10 3,107 25 65 7.42 1,046 24 39 2.50 Math classroom G014 253 9 11 2,822 25 60 6.74 920 24 32 2.20 Physics lab G080 349 19 11 2,897 25 61 6.91 1,167 24 32 2.80 Hum. classroom G072 196 19 6 3,275 24 60 7.82 1,014 23 31 2.42 English G020 156 20 10 2,993 25 61 7.14 763 24 34 1.82 classroom Time-based averages ∼3000 ∼25 ∼63 ∼7.2 ∼1,117 ∼24 ∼37 ∼2.7 %e indoor CO averages are summarized in Table 3. %ese indoor air-quality parameters will be compared %ough the number of students in the English (G020) with those measured before cleaning the AC filters in the following sections. classroom is higher than that in the Humanities (G075) classroom, and the volume of G020 is less than that of the G075 classroom, the highest CO average (1,330 ppm) be- 3.2.1. Indoor CO Levels. %e indoor concentration of CO longs to G075, while the lowest CO average (763 ppm) 2 2 belongs to G020. %is effect is mainly due to the discrepancy gas is a key indicator of the adequacy of the supply of fresh air in buildings including schools. %e ASHRAE recom- of the sampling time during each lesson and during the day. Indoor CO levels at the end of the lesson could be sig- mends an indoor CO standard maximum level that does not exceed the outdoor concentration by more than about nificantly greater than that at the beginning due to con- centration buildup. In G020, the sampling was performed 700 ppm [23]. Keeping in mind that the CO outdoor background (Figure 3) has varied from 404 to 435 ppm (with during the first lesson 8 : 10 to 8 : 19 am as can be seen from Figure 5, while in G075, it was performed in the last lesson an 8-hour average value of ∼419 ppm), the ASHRAE stan- dard maximum would be 1119 ppm (419 + 700 ppm). %is during 1 : 50–2:00 pm. %e same reasoning could be ex- tended to temperature and relative humidity. standard is shown in Figure 6 as a dashed red line. In most of the remaining locations, the CO values %e CO levels before and after cleaning the clogged AC oscillate around the ASHRAE standard (1119 ppm). How- filters are shown in Figure 6. Before cleaning the AC filters, ever, the average value for all measurements is 1117 ppm, the CO levels in all fifteen locations were above the which is below the ASHRAE standard. 1119 ppm AHRAE standard maximum. As can be noticed %e highest temperature average (25 C) belongs to the from Table 3, the CO levels have varied from 2625 ppm in Arabic classroom (G138), while the lowest (23 C) is attained classroom G075 to 3381 ppm in the cafeteria (G106) with an by various classes (G123, G074, and G72). Since the tem- average value of ∼3000 ppm. %is CO concentration cor- th perature varies within a range of 2 C only, nothing can be responds to the 4 danger level listed in Table 1. It would concluded as this discrepancy is close to that of the precision induce headaches, sleepiness, poor concentration, and loss of the temperature sensor. In all locations, the temperature of attention. ° ° curves oscillate between 23 C and 25 C with an average of After cleaning the AC filters, the CO levels have varied ∼24 C. %e temperature curve is stable, and all measurements from 763 ppm in classroom G020 to 1330 ppm in classroom are between the 20 C ASHRAE standard minimum and the G075. %e indoor CO concentrations have exceeded the 27 C ASHRAE standard maximum. 1119 ppm ASHRAE standard maximum slightly in few %e RH curve is relatively variable with the highest classrooms. However, the average indoor CO concentration average (43%) belonging to Chemistry Lab (G123) and the (1117 ppm) is within the recommended 1119 ppm ASHRAE lowest (31%) belonging to the Humanities classroom (G72). standard maximum. %e average RH is ∼37%. All indoor RH oscillates between %e adequacy of ventilation may be measured by the the 30% ASHRAE standard minimum and the 60% ASH- number of cubic feet of air per minute (cfm) provided per RAE standard maximum. person. Alternatively, adequacy of ventilation can be 6 Advances in Meteorology 775 40 940 40 765 34 760 30 28 920 745 20 905 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO 2 2 Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (a) (b) 1022 40 978 45 1014 30 964 20 1006 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO 2 2 Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (c) (d) Figure 5: Continued. Indoor CO levels (ppm) Indoor CO levels (ppm) 2 2 8:49 AM 8:09 AM 8:11 AM 8:51 AM 8:12 AM 8:52 AM 8:13 AM 8:54 AM 8:15 AM 8:55 AM 8:16 AM 8:57 AM 8:18 AM 8:58 AM 8:19 AM 9:00 AM 8:21 AM RH (%) and temperature (°C) RH (%) and temperature (°C) Indoor CO levels (ppm) 2 Indoor CO levels (ppm) 8:24 AM 9:08 AM 8:25 AM 9:10 AM 8:26 AM 9:11 AM 8:28 AM 9:12 AM 8:29 AM 9:14 AM 8:31 AM 9:15 AM 8:32 AM 9:17 AM 8:34 AM 9:18 AM 8:35 AM 9:20 AM RH (%) and temperature (°C) RH (%) and temperature (°C) Advances in Meteorology 7 1040 45 1050 40 1036 40 1032 35 1046 30 1028 30 1024 25 24 1022 22 1020 20 1042 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO 2 2 Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (e) (f ) 1140 45 1053 40 1052 38 1051 36 1120 1050 34 1049 32 1048 30 1047 28 1046 26 1045 24 1044 22 1060 20 1043 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO 2 Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (g) (h) 1210 40 1190 30 1164 24 1170 20 1161 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO 2 2 Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (i) (j) Figure 5: Continued. Indoor CO levels (ppm) Indoor CO levels (ppm) Indoor CO levels (ppm) 2 2 2 11:28 AM 10:29 AM 9:50 AM 11:29 AM 10:30 AM 9:51 AM 11:31 AM 10:32 AM 9:53 AM 11:32 AM 10:33 AM 9:54 AM 11:34 AM 10:35 AM 9:56 AM 11:35 AM 10:36 AM 9:57 AM 11:36 AM 10:37 AM 9:59 AM 11:38 AM 10:39 AM 11:39 AM 10:40 AM 10:00 AM RH (%) and temperature (°C) RH (%) and temperature (°C) RH (%) and temperature (°C) Indoor CO levels (ppm) Indoor CO levels (ppm) Indoor CO levels (ppm) 2 2 2 11:48 AM 10:49 AM 10:09 AM 11:49 AM 10:10 AM 10:50 AM 11:51 AM 10:12 AM 10:52 AM 11:52 AM 10:13 AM 10:53 AM 11:54 AM 10:14 AM 10:55 AM 11:55 AM 10:16 AM 10:56 AM 11:57 AM 10:17 AM 10:58 AM 11:58 AM 10:19 AM 12:00 PM 10:59 AM 10:20 AM RH (%) and temperature (°C) RH (%) and temperature (°C) RH (%) and temperature (°C) 8 Advances in Meteorology 1290 45 40 32 1260 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (k) (l) 1330 45 1314 40 1313 38 1324 1312 36 1311 34 1310 32 1309 30 1308 28 1307 26 1306 24 1305 22 1304 20 1308 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO 2 2 Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (m) (n) 1334 40 1332 35 1330 30 1328 25 1326 20 1324 15 Abu Dhabi local time Indoor CO Indoor temperature (C) Indoor relative humidity (%) (o) Figure 5: Indoor CO levels in ADNOC Schools postcleaning AC filters. (a) Classroom G020, (b) classroom G014, (c) classroom G083, (d) classroom G072, (e) classroom G123, (f ) classroom G087, (g) classroom G138, (h) classroom G106, (i) classroom G080, (j) classroom G009, (k) classroom G074, (l) classroom G134, (m) classroom G008, (n) classroom G132, and (o) classroom G075. Indoor CO levels (ppm) Indoor CO levels (ppm) 2 2 1:09 PM 12:10 PM Indoor CO levels (ppm) 1:10 PM 12:11 PM 1:49 PM 1:12 PM 12:12 PM 1:13 PM 12:14 PM 1:50 PM 1:14 PM 12:15 PM 1:16 PM 12:17 PM 1:52 PM 1:17 PM 12:18 PM 1:19 PM 12:20 PM 1:53 PM 1:20 PM 12:21 PM RH (%) and temperature (°C) RH (%) and temperature (°C) 1:55 PM Indoor CO levels (ppm) Indoor CO levels (ppm) 2 2 1:29 PM 12:28 PM 1:56 PM 1:30 PM 12:30 PM 1:32 PM 12:31 PM 1:58 PM 1:33 PM 12:33 PM 1:35 PM 12:34 PM 1:59 PM 1:36 PM 12:36 PM 1:37 PM 12:37 PM 2:00 PM 1:39 PM 12:38 PM RH (%) and temperature (°C) 1:40 PM 12:40 PM RH (%) and temperature (°C) RH (%) and temperature (°C) Advances in Meteorology 9 3,500 3,000 2,500 2,000 1,500 1,000 G138 G132 G009 G008 G123 G106 G083 G074 G075 G134 G087 G014 G080 G072 G020 Location Indoor CO levels precleaning AC filters Indoor CO levels postcleaning AC filters 1,119 ppm ASHRAE standard max. Figure 6: Indoor CO levels precleaning and postcleaning AC filters in ADNOC Schools. G138 G132 G009 G008 G123 G106 G083 G074 G075 G134 G087 G014 G080 G072 G020 Location Indoor air temperature precleaning AC filters 27 C ASHRAE standard max. Indoor air temperature postcleaning AC filters 20 C ASHRAE standard min. Figure 7: Air temperature indoors of ADNOC Schools precleaning and postcleaning AC filters. G138 G132 G009 G008 G123 G106 G083 G074 G075 G134 G087 G014 G080 G072 G020 Location Indoor relative humidity (%) precleaning AC filters 30% ASHRAE standard min. Indoor relative humidity (%) postcleaning AC filters 60% ASHRAE standard max. Figure 8: Relative humidity indoors of ADNOC Schools precleaning and postcleaning AC filters. evaluated by indoor CO concentrations. For instance, a significantly higher than those with switched-off ventilation. CO level of 1000 ppm is equivalent to 15 cubic feet of fresh CO peaks of ∼3000 ppm in naturally ventilated classrooms 2 2 air per minute per person [17].%us, the indoor CO average have been reported by Corsi et al. [23]. In ADNOC Schools, of 1117 ppm (after cleaning the AC filters) indicates that the though the ventilation is always switched on, with clogged indoor ventilation rates are adequate and healthy for a air filters the situation was equivalent to switched-off ven- learning environment. tilation as the dirt on filters limits or even blocks air cir- An extensive IAQ study by Svitak ´ et al. [24] demon- culation in the classrooms and consequently allows CO to strates that in controlled ventilation, CO levels are build up significantly. Indoor CO levels (ppm) Indoor relative humidity (%) Indoor air temperature (°C) 10 Advances in Meteorology To better quantify the impact of cleaning the AC filters ASHRAE standard minimum and the 60% ASHRAE standard on indoor air quality, indoor-to-outdoor CO ratios have maximum. As can be noticed from Figure 3, the ambient (outdoor) RH measured during the same day has varied from been calculated for all fifteen locations before and after cleaning the AC filters. As can be deduced from Table 3, the 40% at 2 : 21 pm to 77% at 7 : 11 am with an average of∼ 57%. average indoor-to-outdoor CO ratio has been improved %e impact of cleaning the AC filters is evident in Figure 8; it from (3000/419 ≈ 7.2) before cleaning the AC filters to an has decreased the indoor RH from above the ASHRAE average ratio of (1, 117/419 ≈ 2.7) after cleaning, which standard maximum to the vicinity of the ASHRAE standard evidences effectiveness of the corrective actions taken. minimum. %is is due to the fact that a well-cleaned AC system directly lowers the level of RH in classrooms as it circulates the indoor air and removes the excess moisture at 3.2.2. Indoor Air Temperature. Indoor air temperature is a the exhaust of the AC units. %e significant increase in RH key indicator of occupants’ thermal comfort. %e room levels measured before cleaning the AC filters is correlated temperature has a preset value of 23 C in each location with the high CO levels measured simultaneously. %e (Classroom/Lab). To make sure that the HVAC built-in correlation between RH and CO concentrations was re- thermostat maintains the selected temperature, the indoor ported by similar studies, for example, Lazovic et al. [25]. air temperature in each location is monitored by the air meter before and after cleaning the AC filters. It is evident 4. Conclusions from the bar graph of Figure 7 that indoor air temperatures after cleaning the filters are slightly lower than those %is project has identified dirty filters of air-conditioning measured before cleaning the filters. However, the measured units and clogged air intake vents as the main cause of high temperatures (precleaning and postcleaning the AC filters) concentration levels (∼3000 ppm) of carbon dioxide in are all between the recommended 20 C ASHRAE standard several classrooms. After thorough cleaning, an extensive minimum and the 27 C ASHRAE standard maximum, in- indoor air quality assessment has been conducted in fifteen dicating thermally comfortable learning environments. classrooms. %e indoor and outdoor air-quality parameters %ough the indoor environment is thermostat con- of carbon dioxide levels, temperature, and relative humidity trolled, the indoor temperature is significantly impacted by have been monitored simultaneously. During an 8-hour the outdoor ambient temperature. %us, the selection of ambient air quality measurement, it has been observed that 23 C as a preset temperature would allow a logical inves- bus exhaust emissions are the main source of background tigation of the functionalities of both the heating coils and carbon dioxide. %us, few places like bus loading/unloading the cooling chillers of the HVAC units. Figure 3 shows that zones, staff parking lots, and playgrounds were identified as the outdoor air temperature has varied from 21 C at 7 : 11 am hazardous during certain times. Students are advised to wear ° ° to 28 C at 2 : 19 pm with an average of ∼26 C. face masks during these times. Table 3 indicates that before cleaning the AC filters, the %e indoor carbon dioxide levels have varied from ° ° indoor air temperature has varied from 24 C to 27 C with an 763 ppm to 1330 ppm. %e average indoor carbon dioxide average value of∼25 C. After cleaning the AC filters, indoor level for all locations has been estimated to be ∼1117 ppm; ° ° air temperature has varied from 23 C to 25 C with an average below the widely used 1,119 ppm American Society of value of∼24 C. Both averages of air temperature are slightly Heating Refrigerating and Air-Conditioning Engineers higher than the preset value of 23 C. %is slight difference standard maximum. On average, this measurement indicates could be attributed to the locations of the air meter (on the that the indoor ventilation rates are adequate and healthy for student’s desk) and that of the AC monitor. a learning environment. Moreover, the average indoor-to- outdoor carbon dioxide ratio has been improved from 3.2.3. Indoor Relative Humidity. Relative humidity is a key (3000/419 ≈ 7.2) before cleaning the filters of air-condi- indicator of occupants’ thermal comfort. Occupants’ con- tioning units to an average ratio of (1, 117/419 ≈ 2.7) after tribution to RH occurs as a consequence of exhalation. High cleaning, indicating the effectiveness of the corrective ac- RH may cause condensation and mould formation, which is tions taken. unhealthy for occupants and children [22]. %e indoor RH in each location is monitored before and Abbreviations after cleaning the AC filters. As can be noticed from the bar graph of Figure 8, before cleaning the AC filters, the RH in all ADNOC: Abu Dhabi National Oil Company locations (classrooms/labs) oscillates around the 60% ADEC: Abu Dhabi Education Council ASHRAE standard maximum. After cleaning the AC filters, HSE: Health, Safety, and Environment all measurements are between the recommended 30% IAQ: Indoor air quality ASHRAE standard minimum and the 60% ASHRAE stan- WHO: World Health Organization dard maximum. EPA: Environmental Protection Agency As can be seen from Table 3, before cleaning the AC filters, ASHRAE: American Society of Heating Refrigerating and RH has varied from 60% to 69% with an average value of Air-Conditioning Engineers ∼63%, which is above the ASHRAE standard maximum. After NIOSH: National Institute of Occupational Safety and cleaning the AC filters, RH has varied from 31% to 43% with Health an average value of ∼37%, which is well between the 30% HVAC: Heating, ventilation, and air-conditioning units. Advances in Meteorology 11 [12] A. K. Persily, “Evaluating building IAQ and ventilation with Data Availability carbon dioxide,”ASHRAETransactions, vol. 103, pp. 193–204, Our data (experimental results that we have obtained) are [13] D. G. Shendell, R. Prill, W. J. Fisk, M. G. Apte, D. Blake, and shown in the figures listed within the manuscript. Data like D. Faulkner, “Associations between classroom CO concen- standards are referenced wherever used in the body of the trations and student attendance in Washington and Idaho,” manuscript. Indoor Air, vol. 14, no. 5, pp. 333–341, 2004. [14] T. Pietrucha, “Measurement of carbon dioxide concentration for assessment of indoor air quality in the lecture hall,” in Conflicts of Interest Proceedings of the 13th Students’ Science Conference, pp. 17– %e authors declare that there are no conflicts of interest 20, Wroclaw, Lower Silesia, Poland, September 2015. [15] N. Mahyuddin and H. Awbi, “A review of CO2Measurement regarding the publication of this paper. procedures in ventilation research,” International Journal of Ventilation, vol. 10, no. 4, pp. 353–370, 2012. Acknowledgments [16] A. P. Jones, “Indoor air quality and health,” Atmospheric Environment, vol. 33, no. 28, pp. 4535–4564, 1999. %is works was funded, in part, by ADNOC Schools. [17] M. J. Ellenbecker, “Engineering controls for clean air in the office environment,” Clinics in Chest Medicine, vol. 13, no. 2, pp. 193–199, 1992. References [18] American Society of Heating Refrigerating and Air Condi- tioning Engineers (ASHRAE), Standard 62: ventilation for [1] U.S. Environmental Protection Agency, /e Total Exposure acceptable indoor air quality, ASHRAE, Atlanta, GA, USA, Assessment Methodology (TEAM) Study: Summary and Analysis, U.S. Environmental Protection Agency, Wash- [19] American Society of Heating, Refrigerating, and Air-Con- ington, DC, USA, EPA/600/6-87/002a, 1987. ditioning Engineers (ASHRAE), Standard 62.1-2013: venti- [2] U.S. Environmental Protection Agency,ReporttoCongresson lationforacceptableindoorairquality, ASHRAE, Atlanta, GA, Indoor Air Quality, vol. 2, U.S. Environmental Protection USA, 2013. Agency, Washington, DC, USA, 1989, EPA/400/1-89/001C. [20] N. L. Sireesha, “Correlation amongst indoor air quality, [3] EPA-Environmental Protection Agency, IAQ Reference ventilation and carbon dioxide,”JournalofScientificResearch, Guide: Tools for Schools, EPA-Environmental Protection vol. 9, no. 2, pp. 179–192, 2017. Agency, Washington, DC, USA, EPA 402-K-95-001, %ird [21] M. Kavgic, A. Summerfield, D. Mumovic, Z. M. Stevanovic, edition, 2005. V. Turanjanin, and Z. Z. Stevanovic, “Characteristics of in- [4] J. Madureira, I. Paciˆ encia, C. Pereira, J. P. Teixeira, and door temperatures over winter for Belgrade urban dwellings: E. d. O. Fernandes, “Indoor air quality in Portuguese schools: indications of thermal comfort and space heating energy levels and sources of pollutants,” Indoor Air, vol. 26, no. 4, demand,” Energy and Buildings, vol. 47, pp. 506–514, 2012. pp. 526–537, 2016. [22] M. Abuku, H. Janssen, and S. Roels, “Impact of wind-driven [5] M. Simoni, I. Annesi-Maesano, T. Sigsgaard et al., “Rela- rain on historic brick wall buildings in a moderately cold and tionships between school indoor environment and respiratory humid climate: numerical analyses of mould growth risk, health in children of five European countries: HESE study,” indoor climate and energy consumption,” Energy and European Respiratory Journal, vol. 28, p. 837s, 2006. Buildings, vol. 41, no. 1, pp. 101–110, 2009. [6] M. Simoni, I. Annesi-Maesano, T. Sigsgaard et al., “School air [23] R. L. Corsi, V. M. Torres, M. Sanders, and K. A. Kinney, quality related to dry cough, rhinitis and nasal patency in “Carbon dioxide levels and dynamics in elementary schools: children,” European Respiratory Journal, vol. 35, no. 4, results of the TESIAS study,” Proceedings: Indoor Air, vol. 1, pp. 742–749, 2010. pp. 74–79, 2002. [7] M. Takaoka, K. Suzuki, and D. Norback, “Sick building [24] M. Svitak, ´ K. Krontorad, ´ J. Kropa ´cek, ˇ L. Hlaskov ´ a, ´ and syndrome among junior high school students in Japan in A. Solaˇ r, “Parameters of indoor air quality (IAQ) in wooden relation to the home and school environment,”GlobalJournal houses,” BioResources, vol. 13, no. 4, pp. 8222–8238, 2018, of Health Science, vol. 8, no. 2, 2016. ISSN:1930-2126. [8] C. A. Erdmann, K. C. Stener, and M. G. Apte, “Indoor carbon [25] I. M. Lazovic, Z. M. Stevanovic, M. V. Jovasevic-Stojanovic, dioxide concentrations and sick building syndrome symp- M. M. Zivkovic, and M. J. Banjac, “Impact of CO2 concen- toms in the base study revisited: analysis of the 100 building tration on indoor air quality and correlation with relative dataset,” Proceedings: Indoor Air, vol. 3, pp. 443–448, 2002. humidity and indoor air temperature in school buildings, [9] T. Tillet, “Formaldehyde exposure among children: a potential Serbia,” /ermal Science, vol. 20, 2015. building block of asthma,”EnvironmentalHealthPerspectives, vol. 118, p. a131, 2010. [10] M. J. Mendell, E. A. Eliseeva, M. M. Davies, and A. Lobscheid, “Do classroom ventilation rates in California elementary schools influence standardized test scores? results from a prospective study,” Indoor Air, vol. 26, no. 4, pp. 546–557, [11] A. Szczurek, M. Mciejewska, and T. Pietrucha, “CO and volatile organic compounds as indicators of IAQ,” in Pro- ceedings of the 36th AIVC Conference, 5th TightVent Con- ference, 3rd venticool Conference, pp. 23-24, Madrid, Spain, September 2015. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Advances in Meteorology Hindawi Publishing Corporation

Towards Healthy Levels of Carbon Dioxide in Schools of the National Oil Company of Abu Dhabi

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Copyright © 2021 Ali Abu-Rahmah et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Hindawi Advances in Meteorology Volume 2021, Article ID 6680476, 11 pages https://doi.org/10.1155/2021/6680476 Research Article Towards Healthy Levels of Carbon Dioxide in Schools of the National Oil Company of Abu Dhabi 1 1 2 1 AliAbu-Rahmah , RasheedAhmad, AbdelmaoulaHaboub, andYasminAbu-Rahmah ADNOC Schools, Abu Dhabi, UAE Nikon Research Corporation of America, 1399 Shore Way Road, Belmont 94002-4107, CA, USA Correspondence should be addressed to Ali Abu-Rahmah; aliaburahmah@yahoo.com Received 22 December 2020; Revised 17 April 2021; Accepted 14 July 2021; Published 22 July 2021 Academic Editor: Antonio Donateo Copyright © 2021 Ali Abu-Rahmah et al. %is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In their annual indoor air quality assessment for ADNOC Schools, the Abu Dhabi Education Council has reported hazardous levels (∼3000 ppm) of carbon dioxide in fifteen classrooms. Exposure of 5,090 students attending the school for ∼eight hours (typical school day) to such high levels of carbon dioxide would induce adverse health conditions like headaches, drowsiness, and lack of concentration on the short term and serious diseases like asthma and sick building syndrome on the long term. %e Health, Safety, and Environment committee of the school has identified clogged air intake vents and dirty AC filters as the main cause of the high carbon dioxide concentrations reported. %e outdoor (ambient) carbon dioxide level is measured and has an eight-hour average value of 419 ppm. After cleaning thoroughly, the indoor levels of carbon dioxide, temperature, and relative humidity were monitored simultaneously in each classroom and have average values of∼1117 ppm,∼24 C, and∼37%, respectively. In addition, the average indoor-to-outdoor ratio of carbon dioxide has been improved from 3000/419 ≈ 7.2 before cleaning the AC filters to an average ratio of (1, 117/419 ≈ 2.7) after cleaning. %us, ventilation rates in the classrooms monitored in this project are adequate and the corrective actions taken were effective. In particular, children are more sensitive to pollutants than 1. Introduction adults because they have high inhalation rates per body mass Data of the US Environmental Protection Agency (EPA) and their respiratory and immune systems are still devel- indicate that indoor pollution levels may be 2–5 times higher oping [4]. Failure to respond promptly to IAQ problems in than those of outdoor levels [1]. High levels of indoor air schools may lead to short- and long-term respiratory health pollution are of particular interest because it is estimated issues [5] as dry cough, rhinitis, and nasal patency in that people spend most (∼90%) of their times indoors [2]. children [6]; occurrence of sick building syndrome among %e exposure to high levels of indoor air pollutants has students [7, 8]; asthma [9]; and poor academic achievement increased over the past several decades. %is increase may be [10]. attributed to reduction of ventilation rates to save energy; %e adequacy of the supply of fresh air in buildings use of synthetic building materials and furnishings; and use including schools is commonly evaluated by investigating of chemically formulated personal products, pesticides, and the level of carbon dioxide (CO ) concentration in a room cleaning supplies. [11, 12]. %is gas is a natural constituent of the atmosphere In schools, good indoor air quality (IAQ) contributes to and is emitted from humans during exhalation. High a favourable learning environment for students, protects concentration levels of CO indicate poor air quality due to health, and assists with the core mission―education. %e inadequate ventilation. %is may cause students to loss presence of a wide variety of emission sources like art and conscious (fainting), to get headaches, or to function with science supplies makes sustaining good IAQ a challenge [3]. lower activity levels. %e relation between CO 2 2 Advances in Meteorology concentration and student absences was investigated [8, 13]. In ADNOC Schools, a mechanical (SKM, model APCN- %e relation between certain CO concentration levels and 5240Y) HVAC system has been placed on the rooftop. %is the corresponding IAQ effects is summarized by Pietrucha system incorporates bag and metal filters to extract dust [14] in Table 1. from air flowing to the buildings. %e manufacturer rec- ommends a quarterly cleaning for most air filters. However, %e concentration of CO gas in a given sample of air is the UAE has a dusty environment, which demands a more relatively easy to measure [15]. Its concentration is expressed frequent cleaning of AC filters. in units of parts per million (ppm); a ratio that indicates the In resolving the high CO levels reported by the ADEC, number of CO molecules per million molecules of air. 2 2 clogged filters have been cleaned thoroughly and defective Outdoor CO levels must be measured when assessing in- bag filters are replaced. Windows’ rubber frames have been door concentrations because the outdoor CO directly maintained. Figure 1 shows a random AC filter before and impacts the indoor concentration. In outdoor air, CO after cleaning. concentration normally varies from 350 to 450 ppm [16]. Effectiveness of the corrective actions taken in this %e adequacy of ventilation may be measured by the number project has been evaluated by monitoring the CO con- of cubic feet of air per minute (cfm) provided per person. 2 centration levels before and after cleaning the clogged AC Alternatively, adequacy of ventilation can be evaluated by filters. Ten-minute walk-through measurements were taken indoor CO concentrations. For instance, a CO level of 2 2 before and after cleaning the filters. Measurements were 1000 ppm is equivalent to 15 cubic feet of fresh air per made using the portable Fluke model 975 air meter, which minute per person [17]. %e American Society of Heating, monitors CO concentration levels, temperature, and rela- Refrigerating, and Air Conditioning Engineers (ASHRAE) tive humidity simultaneously. %e range, resolution, and has recommended indoor CO levels that do not exceed the accuracy of this instrument are summarized in Table 2 local outdoor concentration by more than about 700 ppm below. [18]. %e ASHRAE standard 62.1–2013 recommends indoor Since the indoor CO concentrations are directly im- CO levels at less than 1000 ppm in schools and 800 ppm in 2 pacted by the outdoor CO levels, the ASHRAE recom- offices [19]. %e National Institute for Occupational Safety mends an indoor CO standard maximum level that does and Health (NIOSH) considers that indoor air concentra- 2 not exceed the outdoor concentration by more than about tions of CO that exceed 1000 ppm are a marker of inad- 700 ppm [23]. %us, another identical air meter was placed equate ventilation [20]. Indoor air temperature (T) and on the rooftop near the inlet of the AC ventilation to relative humidity (RH) are key indicators of occupants’ quantify the background CO levels. Care was taken to place thermal comfort [21]. High RH may cause condensation and air meters in locations that would not be directly impacted mould formation, which is unhealthy for occupants and by the breath of individual children. In each location, the children [22]. meter was placed one meter above the floor at the level of In their annual IAQ walk-through assessment of student desk and about one meter from the walls, away from ADNOC Schools, the Abu Dhabi Education Council doors and windows, thus avoiding possible air disturbances (ADEC) has reported hazardous levels (∼3000 ppm) of CO . as can be noticed in Figure 2. Such high levels of CO would induce adverse health To reach a steady state of occupancy and ventilation, conditions like asthma, headaches, drowsiness, and lack of doors and windows of each classroom are kept locked and a concentration to a large number of personnel (∼6304) reasonable time (∼5 minutes) was allowed before each distributed among 6 campuses of ADNOC Schools. In measurement could be made. Ten-minute measurements particular, 5090 students spending ∼8 hours of their time could be made during lessons (occupied periods). %e code indoors would be affected mostly as their respiratory system number of each classroom is stored in the memory of the air is still developing. %erefore, the Health, Safety, and Envi- meter ahead of measurements. Following this methodology, ronment (HSE) committee of the school has decided to a real-time monitoring of CO levels, temperature, and RH is reduce the reported high CO concentration levels. %e aim 2 made in fifteen locations indoors of the male campus of this study is to evaluate the indoor air quality before and building of ADNOC Schools before and after cleaning of the after a set of corrective actions were taken. AC filters. 2. Methodology 3. Results and Discussion %e environment inside a building can be controlled by a Air quality was evaluated during the typical school day of th system of heating, ventilation, and air-conditioning January 8 2015. Indoor CO concentrations are directly (HVAC). %is system maintains a comfortable humidity impacted by the outdoor (background) CO levels. %us, the level and uses a thermostat to control the air temperature indoor and outdoor CO levels, air temperature (T), and RH inside a room by heating or cooling. %e HVAC system were measured simultaneously. dilutes indoor pollutants with outdoor air. Fans circulate air through filters to extract dust. To supply clean air, an inlet is placed (on roof ) as far as possible from the ground. 3.1. Outdoor Air Quality. %e outside air concentration of However, leaky windows allow dust to clog filters, which CO is measured close to the region where the fresh air is slows air circulation and causes buildup of high CO levels. drawn into the building. An air meter was placed on the 2 Advances in Meteorology 3 Table 1: Description of indoor air quality on the basis of CO concentrations. Indoor CO Description of indoor air quality 350–400 ppm Normal background concentration in outdoor ambient air 400–1,000 ppm Concentrations typical of occupied indoor spaces with good air exchange 1,000–2,000 ppm Complaints of drowsiness and poor air Headaches, sleepiness, and stagnant, stale, stuffy air. Poor concentration, loss of attention, increased heart rate, and 2,000–5,000 ppm slight nausea may also be present 5,000 ppm Workplace exposure limit (as 8-hour TWA) in most jurisdictions >40,000 Exposure may lead to serious oxygen deprivation, resulting in permanent brain damage, coma, even death Precleaning Postcleaning Figure 1: Typical HVAC filter precleaning and postcleaning in ADNOC Schools. Table 2: Accuracy, resolution, and range of Fluke 975 air meter. Measured parameter Range Display resolution Accuracy % of reading CO 0 to 5000 ppm 1 ppm 2.75% + 75 ppm ° ° ° ° ° ° Temperature −20 to 50 C 0.1 C ±0.5 C from 5 C to 40 C Relative humidity 10 to 90% RH 0.1% ±3% RH from 10 to 90% RH background CO levels as referenced to the primary axis of Figure 3, while the ambient temperature in degree Celsius and RH are both measured and referenced to the secondary axis. Outdoor CO concentrations varied from 404 ppm at 9 : 45 am to 435 ppm at 7 : 31 pm with an eight-hour average value of 419 ppm. %is background CO is normal and primarily due to vehicle emissions. Outdoor air temperature ° ° has varied from 21 C at 7 : 11 am to 28 C at 2 : 19 pm with an Air meter Particle counter average of ∼26 C, while the RH has varied from 40% at 2 : (Fluke 975) (Fluke 985) 21 pm to 77% at 7 : 11 am with an average of ∼57%. Bus loading/unloading areas, staff parking lot, swimming pools, and shaded playground shown in Figure 4 are identified Figure 2: Air-quality monitors used in this study. as hazardous zones (for students/staff who are in these areas) during the time intervals 7 : 10–8:00 am and 2 : 30–3:00 pm. central area of the rooftop near the inlet of the AC units. %e %ese zones are all outdoor locations. During bus loading and outdoor air quality has been measured continuously as a unloading times, students and staff who are close to buses are function of Abu Dhabi local time from 7 : 00 am to 3 : 00 pm advised to wear a face mask as they are exposed directly to CO with two-minute intervals. %is measurement monitored the levels that are much higher than those detected on the rooftop. 4 Advances in Meteorology 440 80 420 50 400 20 Abu Dhabi local time Ambient (outdoor) CO Outdoor temperature (C) Outdoor CO average (419 ppm) Relative humidity (%) Figure 3: Outdoor levels of CO , relative humidity, and temperature. Bus loading zones Parking lot Shaded yard Science labs Figure 4: Hazardous zones around the campus of ADNOC Schools. 3.2.IndoorAirQuality. To assess the impact of cleaning AC their average values are represented in the bar graphs of filters on indoor air quality, the indoor CO levels were Figures 6–8. measured before and after cleaning the clogged AC filters in Figure 5 shows data sets of CO levels, air temperature, fifteen locations within the main campus of ADNOC and RH simultaneous measurements in fifteen indoor lo- Schools. %e locations selected include ten classrooms, four cations (Classrooms, Labs) after the cleaning of the AC labs, and one cafeteria. Cafeteria and labs are included as filters. Each graph can be identified with the name and code they represent spaces with different occupancy, area, and of the class/lab. %e indoor CO curves are referenced to the activity levels. Ten-minute walk-through CO , temperature, primary axis, while the indoor air temperature and RH and RH measurements with one-minute increment have curves are referenced to the secondary axis (to the left of each been made; their averages are summarized in Table 3. %e graph). %e graphs are arranged in the same sequence during results are represented by time-series graphs in Figure 5, and the time that data have been collected. Ambient CO levels (ppm) 6:28 AM 6:43 AM 6:57 AM 7:12 AM 7:26 AM 7:40 AM 7:55 AM 8:09 AM 8:24 AM 8:38 AM 8:52 AM 9:07 AM 9:21 AM 9:36 AM 9:50 AM 10:04 AM 10:19 AM 10:33 AM 10:48 AM 11:02 AM 11:16 AM 11:31 AM 11:45 AM 12:00 PM 12:14 PM 12:28 PM 12:43 PM 12:57 PM 1:12 PM 1:26 PM 1:40 PM 1:55 PM 2:09 PM 2:24 PM 2:38 PM 2:52 PM RH (%) and temperature (°C) Advances in Meteorology 5 Table 3: Indoor air-quality parameters precleaning and postcleaning the AC filters. Precleaning AC filters Postcleaning AC filters Vol. No. of Grade CO CO CO 2 2 2 Location Code 3 T RH CO levels T RH (m ) occupants level levels indoor/ indoor/ ° ° ( C) (%) (ppm) ( C) (%) (ppm) outdoor outdoor Arabic classroom G138 238 12 9 2,893 27 63 6.90 1,048 25 38 2.50 Arabic classroom G132 238 17 7 3,098 26 67 7.40 1,318 24 42 3.15 Math classroom G009 253 7 12 2,897 25 63 6.91 1,189 24 37 2.84 English G008 156 8 12 3, 311 25 64 7.90 1,308 24 38 3.12 classroom Chemistry lab G123 140 10 10 2,792 24 69 6.66 1,033 23 43 2.47 Cafeteria G106 756 44 6–12 3,381 25 66 8.00 1,087 24 41 2.60 Physics lab G083 349 13 12 2,778 25 65 6.63 971 24 39 2.32 Hum. classroom G074 196 10 8 3,009 24 65 7.18 1,272 23 41 3.00 Hum. classroom G075 196 13 8 2,625 25 62 6.26 1,330 24 34 3.17 Arabic classroom G134 238 17 7 3,117 25 61 7.44 1,286 24 32 3.07 Art lab G087 349 21 10 3,107 25 65 7.42 1,046 24 39 2.50 Math classroom G014 253 9 11 2,822 25 60 6.74 920 24 32 2.20 Physics lab G080 349 19 11 2,897 25 61 6.91 1,167 24 32 2.80 Hum. classroom G072 196 19 6 3,275 24 60 7.82 1,014 23 31 2.42 English G020 156 20 10 2,993 25 61 7.14 763 24 34 1.82 classroom Time-based averages ∼3000 ∼25 ∼63 ∼7.2 ∼1,117 ∼24 ∼37 ∼2.7 %e indoor CO averages are summarized in Table 3. %ese indoor air-quality parameters will be compared %ough the number of students in the English (G020) with those measured before cleaning the AC filters in the following sections. classroom is higher than that in the Humanities (G075) classroom, and the volume of G020 is less than that of the G075 classroom, the highest CO average (1,330 ppm) be- 3.2.1. Indoor CO Levels. %e indoor concentration of CO longs to G075, while the lowest CO average (763 ppm) 2 2 belongs to G020. %is effect is mainly due to the discrepancy gas is a key indicator of the adequacy of the supply of fresh air in buildings including schools. %e ASHRAE recom- of the sampling time during each lesson and during the day. Indoor CO levels at the end of the lesson could be sig- mends an indoor CO standard maximum level that does not exceed the outdoor concentration by more than about nificantly greater than that at the beginning due to con- centration buildup. In G020, the sampling was performed 700 ppm [23]. Keeping in mind that the CO outdoor background (Figure 3) has varied from 404 to 435 ppm (with during the first lesson 8 : 10 to 8 : 19 am as can be seen from Figure 5, while in G075, it was performed in the last lesson an 8-hour average value of ∼419 ppm), the ASHRAE stan- dard maximum would be 1119 ppm (419 + 700 ppm). %is during 1 : 50–2:00 pm. %e same reasoning could be ex- tended to temperature and relative humidity. standard is shown in Figure 6 as a dashed red line. In most of the remaining locations, the CO values %e CO levels before and after cleaning the clogged AC oscillate around the ASHRAE standard (1119 ppm). How- filters are shown in Figure 6. Before cleaning the AC filters, ever, the average value for all measurements is 1117 ppm, the CO levels in all fifteen locations were above the which is below the ASHRAE standard. 1119 ppm AHRAE standard maximum. As can be noticed %e highest temperature average (25 C) belongs to the from Table 3, the CO levels have varied from 2625 ppm in Arabic classroom (G138), while the lowest (23 C) is attained classroom G075 to 3381 ppm in the cafeteria (G106) with an by various classes (G123, G074, and G72). Since the tem- average value of ∼3000 ppm. %is CO concentration cor- th perature varies within a range of 2 C only, nothing can be responds to the 4 danger level listed in Table 1. It would concluded as this discrepancy is close to that of the precision induce headaches, sleepiness, poor concentration, and loss of the temperature sensor. In all locations, the temperature of attention. ° ° curves oscillate between 23 C and 25 C with an average of After cleaning the AC filters, the CO levels have varied ∼24 C. %e temperature curve is stable, and all measurements from 763 ppm in classroom G020 to 1330 ppm in classroom are between the 20 C ASHRAE standard minimum and the G075. %e indoor CO concentrations have exceeded the 27 C ASHRAE standard maximum. 1119 ppm ASHRAE standard maximum slightly in few %e RH curve is relatively variable with the highest classrooms. However, the average indoor CO concentration average (43%) belonging to Chemistry Lab (G123) and the (1117 ppm) is within the recommended 1119 ppm ASHRAE lowest (31%) belonging to the Humanities classroom (G72). standard maximum. %e average RH is ∼37%. All indoor RH oscillates between %e adequacy of ventilation may be measured by the the 30% ASHRAE standard minimum and the 60% ASH- number of cubic feet of air per minute (cfm) provided per RAE standard maximum. person. Alternatively, adequacy of ventilation can be 6 Advances in Meteorology 775 40 940 40 765 34 760 30 28 920 745 20 905 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO 2 2 Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (a) (b) 1022 40 978 45 1014 30 964 20 1006 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO 2 2 Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (c) (d) Figure 5: Continued. Indoor CO levels (ppm) Indoor CO levels (ppm) 2 2 8:49 AM 8:09 AM 8:11 AM 8:51 AM 8:12 AM 8:52 AM 8:13 AM 8:54 AM 8:15 AM 8:55 AM 8:16 AM 8:57 AM 8:18 AM 8:58 AM 8:19 AM 9:00 AM 8:21 AM RH (%) and temperature (°C) RH (%) and temperature (°C) Indoor CO levels (ppm) 2 Indoor CO levels (ppm) 8:24 AM 9:08 AM 8:25 AM 9:10 AM 8:26 AM 9:11 AM 8:28 AM 9:12 AM 8:29 AM 9:14 AM 8:31 AM 9:15 AM 8:32 AM 9:17 AM 8:34 AM 9:18 AM 8:35 AM 9:20 AM RH (%) and temperature (°C) RH (%) and temperature (°C) Advances in Meteorology 7 1040 45 1050 40 1036 40 1032 35 1046 30 1028 30 1024 25 24 1022 22 1020 20 1042 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO 2 2 Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (e) (f ) 1140 45 1053 40 1052 38 1051 36 1120 1050 34 1049 32 1048 30 1047 28 1046 26 1045 24 1044 22 1060 20 1043 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO 2 Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (g) (h) 1210 40 1190 30 1164 24 1170 20 1161 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO 2 2 Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (i) (j) Figure 5: Continued. Indoor CO levels (ppm) Indoor CO levels (ppm) Indoor CO levels (ppm) 2 2 2 11:28 AM 10:29 AM 9:50 AM 11:29 AM 10:30 AM 9:51 AM 11:31 AM 10:32 AM 9:53 AM 11:32 AM 10:33 AM 9:54 AM 11:34 AM 10:35 AM 9:56 AM 11:35 AM 10:36 AM 9:57 AM 11:36 AM 10:37 AM 9:59 AM 11:38 AM 10:39 AM 11:39 AM 10:40 AM 10:00 AM RH (%) and temperature (°C) RH (%) and temperature (°C) RH (%) and temperature (°C) Indoor CO levels (ppm) Indoor CO levels (ppm) Indoor CO levels (ppm) 2 2 2 11:48 AM 10:49 AM 10:09 AM 11:49 AM 10:10 AM 10:50 AM 11:51 AM 10:12 AM 10:52 AM 11:52 AM 10:13 AM 10:53 AM 11:54 AM 10:14 AM 10:55 AM 11:55 AM 10:16 AM 10:56 AM 11:57 AM 10:17 AM 10:58 AM 11:58 AM 10:19 AM 12:00 PM 10:59 AM 10:20 AM RH (%) and temperature (°C) RH (%) and temperature (°C) RH (%) and temperature (°C) 8 Advances in Meteorology 1290 45 40 32 1260 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (k) (l) 1330 45 1314 40 1313 38 1324 1312 36 1311 34 1310 32 1309 30 1308 28 1307 26 1306 24 1305 22 1304 20 1308 20 Abu Dhabi local time Abu Dhabi local time Indoor CO Indoor CO 2 2 Indoor temperature (C) Indoor temperature (C) Indoor relative humidity (%) Indoor relative humidity (%) (m) (n) 1334 40 1332 35 1330 30 1328 25 1326 20 1324 15 Abu Dhabi local time Indoor CO Indoor temperature (C) Indoor relative humidity (%) (o) Figure 5: Indoor CO levels in ADNOC Schools postcleaning AC filters. (a) Classroom G020, (b) classroom G014, (c) classroom G083, (d) classroom G072, (e) classroom G123, (f ) classroom G087, (g) classroom G138, (h) classroom G106, (i) classroom G080, (j) classroom G009, (k) classroom G074, (l) classroom G134, (m) classroom G008, (n) classroom G132, and (o) classroom G075. Indoor CO levels (ppm) Indoor CO levels (ppm) 2 2 1:09 PM 12:10 PM Indoor CO levels (ppm) 1:10 PM 12:11 PM 1:49 PM 1:12 PM 12:12 PM 1:13 PM 12:14 PM 1:50 PM 1:14 PM 12:15 PM 1:16 PM 12:17 PM 1:52 PM 1:17 PM 12:18 PM 1:19 PM 12:20 PM 1:53 PM 1:20 PM 12:21 PM RH (%) and temperature (°C) RH (%) and temperature (°C) 1:55 PM Indoor CO levels (ppm) Indoor CO levels (ppm) 2 2 1:29 PM 12:28 PM 1:56 PM 1:30 PM 12:30 PM 1:32 PM 12:31 PM 1:58 PM 1:33 PM 12:33 PM 1:35 PM 12:34 PM 1:59 PM 1:36 PM 12:36 PM 1:37 PM 12:37 PM 2:00 PM 1:39 PM 12:38 PM RH (%) and temperature (°C) 1:40 PM 12:40 PM RH (%) and temperature (°C) RH (%) and temperature (°C) Advances in Meteorology 9 3,500 3,000 2,500 2,000 1,500 1,000 G138 G132 G009 G008 G123 G106 G083 G074 G075 G134 G087 G014 G080 G072 G020 Location Indoor CO levels precleaning AC filters Indoor CO levels postcleaning AC filters 1,119 ppm ASHRAE standard max. Figure 6: Indoor CO levels precleaning and postcleaning AC filters in ADNOC Schools. G138 G132 G009 G008 G123 G106 G083 G074 G075 G134 G087 G014 G080 G072 G020 Location Indoor air temperature precleaning AC filters 27 C ASHRAE standard max. Indoor air temperature postcleaning AC filters 20 C ASHRAE standard min. Figure 7: Air temperature indoors of ADNOC Schools precleaning and postcleaning AC filters. G138 G132 G009 G008 G123 G106 G083 G074 G075 G134 G087 G014 G080 G072 G020 Location Indoor relative humidity (%) precleaning AC filters 30% ASHRAE standard min. Indoor relative humidity (%) postcleaning AC filters 60% ASHRAE standard max. Figure 8: Relative humidity indoors of ADNOC Schools precleaning and postcleaning AC filters. evaluated by indoor CO concentrations. For instance, a significantly higher than those with switched-off ventilation. CO level of 1000 ppm is equivalent to 15 cubic feet of fresh CO peaks of ∼3000 ppm in naturally ventilated classrooms 2 2 air per minute per person [17].%us, the indoor CO average have been reported by Corsi et al. [23]. In ADNOC Schools, of 1117 ppm (after cleaning the AC filters) indicates that the though the ventilation is always switched on, with clogged indoor ventilation rates are adequate and healthy for a air filters the situation was equivalent to switched-off ven- learning environment. tilation as the dirt on filters limits or even blocks air cir- An extensive IAQ study by Svitak ´ et al. [24] demon- culation in the classrooms and consequently allows CO to strates that in controlled ventilation, CO levels are build up significantly. Indoor CO levels (ppm) Indoor relative humidity (%) Indoor air temperature (°C) 10 Advances in Meteorology To better quantify the impact of cleaning the AC filters ASHRAE standard minimum and the 60% ASHRAE standard on indoor air quality, indoor-to-outdoor CO ratios have maximum. As can be noticed from Figure 3, the ambient (outdoor) RH measured during the same day has varied from been calculated for all fifteen locations before and after cleaning the AC filters. As can be deduced from Table 3, the 40% at 2 : 21 pm to 77% at 7 : 11 am with an average of∼ 57%. average indoor-to-outdoor CO ratio has been improved %e impact of cleaning the AC filters is evident in Figure 8; it from (3000/419 ≈ 7.2) before cleaning the AC filters to an has decreased the indoor RH from above the ASHRAE average ratio of (1, 117/419 ≈ 2.7) after cleaning, which standard maximum to the vicinity of the ASHRAE standard evidences effectiveness of the corrective actions taken. minimum. %is is due to the fact that a well-cleaned AC system directly lowers the level of RH in classrooms as it circulates the indoor air and removes the excess moisture at 3.2.2. Indoor Air Temperature. Indoor air temperature is a the exhaust of the AC units. %e significant increase in RH key indicator of occupants’ thermal comfort. %e room levels measured before cleaning the AC filters is correlated temperature has a preset value of 23 C in each location with the high CO levels measured simultaneously. %e (Classroom/Lab). To make sure that the HVAC built-in correlation between RH and CO concentrations was re- thermostat maintains the selected temperature, the indoor ported by similar studies, for example, Lazovic et al. [25]. air temperature in each location is monitored by the air meter before and after cleaning the AC filters. It is evident 4. Conclusions from the bar graph of Figure 7 that indoor air temperatures after cleaning the filters are slightly lower than those %is project has identified dirty filters of air-conditioning measured before cleaning the filters. However, the measured units and clogged air intake vents as the main cause of high temperatures (precleaning and postcleaning the AC filters) concentration levels (∼3000 ppm) of carbon dioxide in are all between the recommended 20 C ASHRAE standard several classrooms. After thorough cleaning, an extensive minimum and the 27 C ASHRAE standard maximum, in- indoor air quality assessment has been conducted in fifteen dicating thermally comfortable learning environments. classrooms. %e indoor and outdoor air-quality parameters %ough the indoor environment is thermostat con- of carbon dioxide levels, temperature, and relative humidity trolled, the indoor temperature is significantly impacted by have been monitored simultaneously. During an 8-hour the outdoor ambient temperature. %us, the selection of ambient air quality measurement, it has been observed that 23 C as a preset temperature would allow a logical inves- bus exhaust emissions are the main source of background tigation of the functionalities of both the heating coils and carbon dioxide. %us, few places like bus loading/unloading the cooling chillers of the HVAC units. Figure 3 shows that zones, staff parking lots, and playgrounds were identified as the outdoor air temperature has varied from 21 C at 7 : 11 am hazardous during certain times. Students are advised to wear ° ° to 28 C at 2 : 19 pm with an average of ∼26 C. face masks during these times. Table 3 indicates that before cleaning the AC filters, the %e indoor carbon dioxide levels have varied from ° ° indoor air temperature has varied from 24 C to 27 C with an 763 ppm to 1330 ppm. %e average indoor carbon dioxide average value of∼25 C. After cleaning the AC filters, indoor level for all locations has been estimated to be ∼1117 ppm; ° ° air temperature has varied from 23 C to 25 C with an average below the widely used 1,119 ppm American Society of value of∼24 C. Both averages of air temperature are slightly Heating Refrigerating and Air-Conditioning Engineers higher than the preset value of 23 C. %is slight difference standard maximum. On average, this measurement indicates could be attributed to the locations of the air meter (on the that the indoor ventilation rates are adequate and healthy for student’s desk) and that of the AC monitor. a learning environment. Moreover, the average indoor-to- outdoor carbon dioxide ratio has been improved from 3.2.3. Indoor Relative Humidity. Relative humidity is a key (3000/419 ≈ 7.2) before cleaning the filters of air-condi- indicator of occupants’ thermal comfort. Occupants’ con- tioning units to an average ratio of (1, 117/419 ≈ 2.7) after tribution to RH occurs as a consequence of exhalation. High cleaning, indicating the effectiveness of the corrective ac- RH may cause condensation and mould formation, which is tions taken. unhealthy for occupants and children [22]. %e indoor RH in each location is monitored before and Abbreviations after cleaning the AC filters. As can be noticed from the bar graph of Figure 8, before cleaning the AC filters, the RH in all ADNOC: Abu Dhabi National Oil Company locations (classrooms/labs) oscillates around the 60% ADEC: Abu Dhabi Education Council ASHRAE standard maximum. After cleaning the AC filters, HSE: Health, Safety, and Environment all measurements are between the recommended 30% IAQ: Indoor air quality ASHRAE standard minimum and the 60% ASHRAE stan- WHO: World Health Organization dard maximum. EPA: Environmental Protection Agency As can be seen from Table 3, before cleaning the AC filters, ASHRAE: American Society of Heating Refrigerating and RH has varied from 60% to 69% with an average value of Air-Conditioning Engineers ∼63%, which is above the ASHRAE standard maximum. After NIOSH: National Institute of Occupational Safety and cleaning the AC filters, RH has varied from 31% to 43% with Health an average value of ∼37%, which is well between the 30% HVAC: Heating, ventilation, and air-conditioning units. Advances in Meteorology 11 [12] A. K. Persily, “Evaluating building IAQ and ventilation with Data Availability carbon dioxide,”ASHRAETransactions, vol. 103, pp. 193–204, Our data (experimental results that we have obtained) are [13] D. G. Shendell, R. Prill, W. J. Fisk, M. G. Apte, D. Blake, and shown in the figures listed within the manuscript. Data like D. 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Advances in MeteorologyHindawi Publishing Corporation

Published: Jul 22, 2021

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