Ventilation Rates In Classrooms Research Articles

Assessing classroom ventilation rates using CO2 data from a nationwide study of UK schools and identifying school-wide correlation factors

Per-person ventilation rates were assessed from data measured in 322 UK schools throughout the Autumn term, 2023. It was found that the overall mean ventilation rate was 5.3 L s−1 p−1; rising to 6.8 L s−1 p−1 during warmer weather and falling to 3.8 L s−1 p−1 during colder weather. Daily mean CO2 levels recorded in the majority of schools consistently fell below the 1500 ppm threshold within government school ventilation guidance but the contribution of relatively few very high CO2 levels in some classrooms shows the need for targeted improvement and highlights the value of large-scale datasets. Exceedance of the 1500 ppm threshold rose to approximately 20% when the daily mean outdoor temperature fell to around 5 °C, indicating a barrier to ventilation. Controlling for outdoor temperature as a covariate, analysis of the CO2 measurements indicated schools in more-deprived regions, state-funded schools (relative to private), and secondary schools (relative to primary) exhibited statistically-significant higher CO2 concentration. Reassuringly, these findings remained unchanged when the analysis was deployed on estimated per-person ventilation rates; except that this enhanced analysis accounted for the greater CO2 production associated with older children and demonstrated that ventilation rates were not significantly different between primary and secondary schools.

Year long monitoring of indoor air quality and ventilation in school classrooms in Victoria, Australia

Children under 15 years spend over six hours per day in school buildings and are particularly vulnerable to the effects of poor indoor air quality (IAQ). However long-term monitoring of indoor environmental conditions is limited in Australian schools. This study evaluates IAQ in ten Australian school classrooms in the temperate settings of Victoria. Temperature, relative humidity, CO2 concentration, PM2.5 and PM10 were monitored over a period of one year. The temperature and relative humidity values in the monitored classrooms ranged between 18.7°C and 23.8°C and 44–63 RH%, respectively, indicating that the conditions have been mechanically controlled. The average air change (ACH) rates in the 10 school classrooms varied considerably (range: 0.7–4.83 ACH). The ventilation rates ranged from 1.6 Ls−1 to 11.5 Ls−1 per person with 7 out of the 10 classrooms showing ventilation rates below the recommended minimum. This study points to the need for increasing ventilation rates in classrooms.

Uncertainty analysis of various CO2-Based tracer-gas methods for estimating seasonal ventilation rates in classrooms with different mechanical systems

Indoor air quality (IAQ) data of 220 classrooms in the Midwestern region of the US were measured during 2015–2017. During three seasons (fall, winter, and spring), indoor and outdoor CO2 concentrations of each classroom were measured under both occupied and unoccupied conditions. To calculate ventilation rates from the collected CO2 data, three main methods derived from the mass-balance equation were used: (1) steady-state; (2) decay rate; and (3) build-up. Since the uncertainty of the individual measurement parameter affects the accuracy or reliability of the calculated, an uncertainty analysis was performed for all three methods. The uncertainty of the estimated ventilation rates in relation to the volume of the classroom, indoor and outdoor CO2 levels, and estimated student CO2 emission rates were determined. The study shows that the steady-state method has the least uncertainty in ventilation rate calculations, while the decay and build-up methods had the lowest and highest values for ventilation rates, respectively. The results also show the estimated ventilation has a larger variance in single-zone systems than in multiple-zone systems. In field measurements, CO2 readings contribute to the largest portion of uncertainty for all three methods. Therefore, with CO2 as the tracer gas, improving the accuracy of CO2 measurement should receive the highest priority for study.

Development of a low-cost air sensor package and indoor air quality monitoring in a California middle school: Detection of a distant wildfire

ABSTRACTA low-cost air sensor package was used to monitor indoor air quality (IAQ) in a classroom at the Albany Middle School in the San Francisco Bay Area of California. A rapid increase in carbon dioxide (CO2) was observed in the classroom as soon as it is occupied. When the classroom is unoccupied, the CO2 levels decay slowly toward the outdoor background level. All high CO2 concentrations observed inside the classroom, above the outdoor background, was due to exhaling of the occupants. The CO2 concentrations generally exceed the recommended level of 1000 ppb towards the end of the school day. The exceedances and slow decay may suggest that the ventilation rate in this school is not sufficient. The particulate level in the classroom was low until a distant wildfire advected large amount of particulate matter to the San Francisco Bay Area. Very high (10–15 times compared to the background) particle numbers (per m3 of particles with diameter >0.3 µm) were observed in the classroom during the wildfire. These particles were relatively small (0.3–1.0 µm) and the filters (MERV 8) of the ventilation system were unable to filter them out. Therefore, the measurements made by low-cost particle counters can inform the school administrators of adverse IAQ during future wildfire (or other combustion) events. The particle number was independent of the occupation before and during the wildfire suggesting that all observed particles were infiltrated into the classroom from outside. Consistent with previous studies, no appreciable increase in the local ambient CO2 background was observed during this distant wildfire event.Implications: Low-cost air sensors are effective in monitoring indoor air quality in classrooms. The CO2 levels in classrooms are mainly generated indoors due to exhalation of occupants. Concentration of CO2 generally exceed the recommended level of 1000 ppb towards the end of the school day. In contrast, the particulate matter mostly comes from outdoors and small particles penetrate though the filters normally used at schools. Distant wildfires do not increase the local CO2 background appreciably, but significantly increase the particulate matter concentrations both indoors and outdoors. Further investigations are needed to assure that ventilation rates in classrooms are sufficiently health protective.

The ventilation problem in schools: literature review.

Based on a review of literature published in refereed archival journals, ventilation rates in classrooms often fall far short of the minimum ventilation rates specified in standards. There is compelling evidence, from both cross-sectional and intervention studies, of an association of increased student performance with increased ventilation rates. There is evidence that reduced respiratory health effects and reduced student absence are associated with increased ventilation rates. Increasing ventilation rates in schools imposes energy costs and can increase heating, ventilating, and air-conditioning system capital costs. The net annual costs, ranging from a few dollars to about 10 dollars per person, are less than 0.1% of typical public spending on elementary and secondary education in the United States. Such expenditures seem like a small price to pay given the evidence of health and performance benefits.

Do classroom ventilation rates in California elementary schools influence standardized test scores? Results from a prospective study

Limited evidence has associated lower ventilation rates (VRs) in schools with reduced student learning or achievement. We analyzed longitudinal data collected over two school years from 150 classrooms in 28 schools within three California school districts. We estimated daily classroom VRs from real-time indoor carbon dioxide measured by web-connected sensors. School districts provided individual-level scores on standard tests in Math and English, and classroom-level demographic data. Analyses assessing learning effects used two VR metrics: average VRs for 30days prior to tests, and proportion of prior daily VRs above specified thresholds during the year. We estimated relationships between scores and VR metrics in multivariate models with generalized estimating equations. All school districts had median school-year VRs below the California VR standard. Most models showed some positive associations of VRs with test scores; however, estimates varied in magnitude and few 95% confidence intervals excluded the null. Combined-district models estimated statistically significant increases of 0.6 points (P=0.01) on English tests for each 10% increase in prior 30-day VRs. Estimated increases in Math were of similar magnitude but not statistically significant. Findings suggest potential small positive associations between classroom VRs and learning.

ISIAQ Academy Awards 2014

Editorial for Indoor Air (Vol. 24, Issue 5, October 2014) WW Nazaroff et al. ISIAQ Academy Awards 2014 The 13 th International Conference on Indoor Air Quality and Climate (Indoor Air 2014) was convened in Hong Kong during the week of 7-12 July 2014. Professor Yuguo Li served as the Conference President. One of many highlights during the conference was the presentation of awards from the ISIAQ Academy of Fellows, which occurred during the opening plenary session. These awards celebrate high achievements in the indoor air sciences. As described in an earlier editorial (Nazaroff, 2012a), the ISIAQ Academy of Fellows has its origins in the creation of the International Academy of Indoor Air Sciences in 1991. In 2005, that organization was reconstituted as a part of the International Society of Indoor Air Quality and Climate (ISIAQ). The ISIAQ Academy of Fellows is an international, multidisciplinary, scientific, honorific organization established to promote scholarship in the indoor environment and building sciences. The awards program, which is featured at all Indoor Air conferences, is a core activity of the Academy. Best Paper Awards The best-papers jury reviewed 143 papers that were published in Indoor Air during the years 2011-2013. Papers were judged for originality, scientific and technical content, and importance. In addition to these criteria, writing style was taken into consideration. The three winning papers each describe the results of field studies. It is noteworthy that two of these papers address what the jury considers to be the most important indoor air quality problem: exposures and health risks associated with indoor biomass cooking. In chronological order, these are the winning papers: • Haverinen-Shaughnessy, U., Moschandreas, D.J. and Shaughnessy, R.J. (2011) Association between substandard classroom ventilation rates and students’ academic achievement, Indoor Air 21, 121-131. This study used a cost-effective design to explore the relationship between classroom ventilation (estimated from CO 2 measurement in one classroom per school) and fifth-grade students passing mandatory standardized tests as a measure of student academic performance. The results are policy relevant, suggesting that increasing the ventilation rates in the many underventilated classrooms toward the recommended guideline values could translate into improved academic achievement of the students. The paper received high scores for originality and importance. • Dutta, A., Mukherjee, B., Das, D., Banerjee, A. and Ray, M.R. (2011) Hypertension with elevated levels of oxidized low-density lipoprotein and anticardiolipin antibody in the circulation of premenopausal Indian women chronically exposed to biomass smoke during cooking, Indoor Air 21, 165-176. In this well-designed study it is shown that poor women in rural India have a high risk of developing cardiovascular diseases. The methods employed are state-of-the-art, including numerous objective measures or signs of health. The paper leaves the reader with a solid impression of excellent science and craftsmanship. The paper scored high in all of the three main criteria. • Hawley, B. and Volckens, J. (2013) Proinflammatory effects of cookstove emissions on human bronchial epithelial cells, Indoor Air 23, 4-13. Another well designed study on effects of biomass cookstoves. The study uses human bronchial epithelial cells to assess pro- inflammatory effects with exposure to either traditional or improved (cleaner burning) cookstove emissions. The results support other evidence indicating that efficient cookstoves can reduce the health burden associated with exposure to household pollution from combustion of solid biomass fuels. The study uses multiple assays to assess effects; the work

Indoor environmental quality in school buildings, and the health and wellbeing of students

Poor indoor environmental quality (IEQ) in classrooms may be a risk for health symptoms and cause absence from school. We conducted a comprehensive study in order to assess the connection between IEQ in Finnish elementary school buildings and the health and academic performance of sixth grade students. The specific aim of the present paper was to study the school- or grade-level prevalence of symptoms in relation to IEQ. The school- or grade-level (i.e. group level) prevalence of self-reported symptoms and perceived IEQ was studied using data collected by a health questionnaire comprising 37 questions. The health questionnaire was sent to all 6th grade students in a stratified random sample of 355 elementary schools in Finland. Indoor environmental conditions were assessed with measurements of ventilation rate and thermal conditions of classrooms in a subsample of 56 schools. Altogether 297 elementary schools participated in the health questionnaire study and a total of 4248 questionnaires were returned (estimated response rate 62.6%). The most common weekly symptoms in the spring semester were fatigue (7.7%), stuffy nose (7.3%), and headache (5.5%). However, both mean prevalence values for different symptoms among all 6th grade students and group-level prevalence values for specific symptoms varied considerably. On the group level, the prevalence values most frequently found above 95% CI (calculated for N=15) were wheezing, cough with wheezing, and fever over 37°C. The most frequently reported IEQ factors causing daily inconvenience in classrooms were noise (11.0%) and stuffy air/poor indoor air quality (IAQ) (7.0%), which were also found most frequently above 95% CI on the group level (calculated for N=15), together with self-reported high indoor temperature and dust or dirtiness. Self-reported daily stuffiness/poor IAQ was significantly correlated with measured mean temperatures and ventilation rates in classrooms. High prevalence of students' self-reported stuffiness/poor IAQ may indicate high indoor temperature or low ventilation rate in classrooms. Also high group level prevalence of other IEQ factors and certain symptoms may be indicative of IEQ problems that should be further studied. The results of this study can be used as a reference for assessing the questionnaire-based prevalence of self-reported symptoms among 6th graders, and their association with IEQ in classrooms. For such assessment, the number of students responding to the questionnaire must be carefully considered, also bearing in mind that prevalence values are symptom specific.

Ventilation system type, classroom environmental quality and pupils' perceptions and symptoms

The present study investigated indoor climate and window opening behaviour by pupils, as well as their perceptions and symptoms in classrooms with different types of ventilation systems. Four classrooms were selected in the same school in suburban Denmark. Classroom ventilation was achieved either by manually operable windows, or by automatically operable windows with and without an exhaust fan in operation, or by a balanced mechanical ventilation system. Indoor air temperature, relative humidity, carbon dioxide (CO2) concentration and window opening were continuously monitored for one month in non-heating and heating seasons; CO2 concentration was used to estimate average classroom ventilation rates. At the end of each measuring period, the pupils were asked to report their perceptions of the indoor environment and their acute health-related symptoms. The classroom in which ventilation was achieved by manually operable windows had the highest air temperatures and CO2 concentrations during both non-heating and heating season; the estimated average air-change rate was lowest in this classroom. The classroom with mechanical ventilation had the highest estimated average air-change rate. Windows were frequently opened in all four classrooms in the non-heating season but very seldom in the heating season. Automatic operation of the windows had a marked effect on CO2 concentration and classroom temperature in the heating season. Perceptions of the indoor environment were more positive in the classroom that was ventilated by automatically operable windows with an exhaust fan in operation: fewer symptoms were reported in this classroom compared with classrooms with other systems. Present results and approach can be used as the basis for rational selection of systems that ensure adequate classroom ventilation.

Association of Lower Classroom Ventilation Rates with Increased Illness Absence in a Prospective Study of California Elementary Schools

Background: Limited evidence associates inadequate classroom ventilation rates (VRs) with increased illness-related absence (IRA) in students. Aims: The goal of this research was to characterize VR...

Association of classroom ventilation with reduced illness absence: a prospective study in California elementary schools

Limited evidence associates inadequate classroom ventilation rates (VRs) with increased illness absence (IA). We investigated relationships between VRs and IA in California elementary schools over two school years in 162 3rd–5th‐grade classrooms in 28 schools in three school districts: South Coast (SC), Bay Area (BA), and Central Valley (CV). We estimated relationships between daily IA and VR (estimated from two year daily real‐time carbon dioxide in each classroom) in zero‐inflated negative binomial models. We also compared IA benefits and energy costs of increased VRs. All school districts had median VRs below the 7.1 l/s‐person California standard. For each additional 1 l/s‐person of VR, IA was reduced significantly (p<0.05) in models for combined districts (−1.6%) and for SC (−1.2%), and nonsignificantly for districts providing less data: BA (−1.5%) and CV (−1.0%). Assuming associations were causal and generalizable, increasing classroom VRs from the California average (4 l/s‐person) to the State standard would decrease IA by 3.4%, increase attendance‐linked funding to schools by $33 million annually, and increase costs by only $4 million. Further increasing VRs would provide additional benefits. These findings, while requiring confirmation, suggest that increasing classroom VRs above the State standard would substantially decrease illness absence and produce economic benefits.

Winter Ventilation Rates at Primary Schools: Comparison Between Portugal and Finland

This study focused on examination of ventilation rates in classrooms with two different types of ventilation systems: natural and mechanical. Carbon dioxide (CO2) measurements were conducted in primary schools of Portugal characterized by natural ventilation and compared to Finland where mechanical ventilation is the norm. The winter period was selected since this season exerts a great influence in naturally ventilated classrooms, where opening of windows and doors occurs due to outdoor atmospheric conditions. The ventilation rates were calculated by monitoring CO2 concentrations generated by the occupants (used as a tracer gas) and application of the buildup phase method. A comparison between both countries' results was conducted with respect to ventilation rates and how these levels corresponded to national regulatory standards. Finnish primary schools (n = 2) registered a mean ventilation rate of 13.3 L/s per person, which is higher than the recommended ventilation standards. However, the Finnish classroom that presented the lowest ventilation rate (7.2 L/s per person) displayed short-term CO2 levels above 1200 ppm, which is the threshold limit value (TLV) recommended by national guidelines. The Portuguese classrooms (n = 2) showed low ventilation rates with mean values of 2.4 L/s per person, which is markedly lower than the minimum recommended value of 7 L/s per person as defined by ASHRAE and 20% less than the REHVA minimum of 3 L/s per person. Carbon dioxide levels of 1000 ppm, close to the TLV of 1200 ppm, were also reached in both Portuguese classrooms studied. The situation in Portugal indicates a potentially serious indoor air quality problem and strengthens the need for intervention to improve ventilation rates in naturally ventilated classrooms.

Novel second-degree solution to single zone mass-balance equation improves the use of build-up data in estimating ventilation rates in classrooms

Recent advances in international guidelines for indoor air quality and on-going work on guidelines for ventilation in Europe increase the need for routinely applicable measurement methods for indoor air quality and ventilation. Ventilation is the key determinant of the behaviour of pollution from both indoors and outdoors in buildings and therefore should be measured together with other indicators of indoor air quality. Various methods have been proposed to measure ventilation rates in different types of buildings. Utilizing carbon dioxide as a marker substance and applying several ventilation phase-based methods together allows for recognizing air recirculation and quantifying CO 2 emission levels that have been identified as challenges in CO 2 -based methods, as well estimating the intrinsic variability of ventilation rates over various levels of occupancy. In schools CO 2 based estimation of ventilation has often been applied to decay phase only, which is not representative of exposure of the school children while using time periods when the classroom is not occupied and when the ventilation may be enhanced, e.g., by opening windows. This paper presents a novel solution to the mass-balance equation facilitating the use of the build-up phase to solve air exchange rates. The new equation allows to avoid impacts of device calibration errors and in combination with previously used steady state and decay methods improves significantly representativity of ventilation estimates in schools. Practical implications Combined use of occupancy phase based ventilation assessment method improves the quality of CO 2 -based estimates of ventilation alone and as part of more comprehensive indoor environmental quality measurements.

Ventilation rates in schools and pupils’ performance

This paper is a development of our earlier work [5,6,11]. The effects of classroom ventilation on pupils’ performance were investigated in 8 primary schools in England. In each school the concentrations of carbon dioxide and other parameters were monitored for three weeks in two selected classrooms. In 16 classrooms interventions were made to improve the ventilation rate and maintain the temperature within an acceptable range using a purpose-built portable mechanical ventilation system. As a result of the interventions the provision of outdoor air to the classrooms was improved from the prevailing levels of about 1 l/s per person to about 8 l/s per person. The pupils and teachers in the classrooms studied were usually exposed to unacceptably poor air quality conditions, with CO 2 concentrations of up to 5000 ppm, much higher than the average recommended levels of 1500 ppm and the preferred level of 1000 ppm. The results of computerized performance tasks performed by more than 200 pupils showed significantly faster and more accurate responses for Choice Reaction (by 2.2%), Colour Word Vigilance (by 2.7%), Picture Memory (by 8%) and Word Recognition (by 15%) at the higher ventilation rates compared with the low ventilation conditions. The present investigation provides strong evidence that low ventilation rates in classrooms significantly reduce pupils’ attention and vigilance, and negatively affect memory and concentration. The physical environment therefore affects teaching and learning.

Association between substandard classroom ventilation rates and students’ academic achievement

This study focuses on the relationship between classroom ventilation rates and academic achievement. One hundred elementary schools of two school districts in the southwest United States were included in the study. Ventilation rates were estimated from fifth-grade classrooms (one per school) using CO(2) concentrations measured during occupied school days. In addition, standardized test scores and background data related to students in the classrooms studied were obtained from the districts. Of 100 classrooms, 87 had ventilation rates below recommended guidelines based on ASHRAE Standard 62 as of 2004. There is a linear association between classroom ventilation rates and students' academic achievement within the range of 0.9-7.1 l/s per person. For every unit (1 l/s per person) increase in the ventilation rate within that range, the proportion of students passing standardized test (i.e., scoring satisfactory or above) is expected to increase by 2.9% (95%CI 0.9-4.8%) for math and 2.7% (0.5-4.9%) for reading. The linear relationship observed may level off or change direction with higher ventilation rates, but given the limited number of observations, we were unable to test this hypothesis. A larger sample size is needed for estimating the effect of classroom ventilation rates higher than 7.1 l/s per person on academic achievement. The results of this study suggest that increasing the ventilation rates toward recommended guideline ventilation rates in classrooms should translate into improved academic achievement of students. More studies are needed to fully understand the relationships between ventilation rate, other indoor environmental quality parameters, and their effects on students' health and achievement. Achieving the recommended guidelines and pursuing better understanding of the underlying relationships would ultimately support both sustainable and productive school environments for students and personnel.

A preliminary study on the association between ventilation rates in classrooms and student performance

Poor conditions leading to substandard indoor air quality (IAQ) in classrooms have been frequently cited in the literature over the past two decades. However, there is limited data linking poor IAQ in the classrooms to student performance. Whereas, it is assumed that poor IAQ results in reduced attendance and learning potential, and subsequent poor student performance, validating this hypothesis presents a challenge in today's school environment. This study explores the association between student performance on standardized aptitude tests that are administered to students on a yearly basis, to classroom carbon dioxide (CO2) concentrations, which provide a surrogate of ventilation being provided to each room. Data on classroom CO2 concentrations (over a 4-5 h time span within a typical school day) were recorded in fifth grade classrooms in 54 elementary schools within a school district in the USA. Results from this preliminary study yield a significant (P < 0.10) association between classroom-level ventilation rate and test results in math. They also indicate that non-linear effects may need to be considered for better representation of the association. A larger sample size is required in order to draw more definitive conclusions. Practical Implications Future studies could focus on (1) gathering more evidence on the possible association between classroom ventilation rates and students' academic performance; (2) the linear/non-linear nature of the association; and (3) whether it is possible to detect 'no observed adverse effect level' for adequate ventilation with respect to academic performance in schools. All of this information could be used to improve guidance and take regulatory actions to ensure adequate ventilation in schools. The high prevalence of low ventilation rates, combined with the growing evidence of the positive impact that sufficient ventilation has on human performance, suggests an opportunity for improving design and management of school facilities.