Risk Factors in Heating, Ventilating, and Air-Conditioning Systemsfor Occupant Symptoms in U.S. Office Buildings: the EPA BASE Study

Abstract

Background: Nonspecific building-related symptoms among occupants of modern office buildings worldwide are common and may be associated with important reductions in work performance, but their etiology remains uncertain. Characteristics of heating, ventilating, and air-conditioning (HVAC) systems in office buildings that increase risk of indoor contaminants or reduce effectiveness of ventilation may cause adverse exposures and subsequent increase in these symptoms among occupants.Methods: We analyzed data collected by the U.S. Environmental Protection Agency (EPA) from a representative sample of 100 large U.S. office buildings -the Building Assessment and Survey Evaluation (BASE) study -using multivariate-adjusted logistic regression models with generalized estimating equations. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) for associations between seven building-related symptom outcomes and selected HVAC system characteristics (excluding ventilation rate, analyzed elsewhere) in the 97 airconditioned study buildings.Results: Among factors of HVAC design or configuration: Outdoor air intakes less than 60 m above the ground were associated with substantially increased odds of most symptoms assessed (ORs up to 2.7). Among factors of HVAC condition, maintenance, or operation: the presence of humidification systems in good condition was associated with reduction in skin symptoms (OR=0.5), whereas the presence of humidification systems in poor condition was associated with increases in upper respiratory symptoms, eye symptoms, fatigue/difficulty concentrating, and skin symptoms (ORs=1.5 to 1.7). Lack of regularly scheduled inspections for HVAC components was associated with increased eye and upper respiratory symptoms (ORs=2.2, 1.6). Less frequent cleaning of cooling coils or condensate drain pans was associated with increased headache and eye symptoms (ORs=1.5, 1.5). Ventilation for 10-12 hours per day (relative to more) was associated with a general slight increase in symptoms, especially fatigue/difficulty concentrating (OR=1.3). Several specific associations opposite of predicted were found, such as with cleanliness of air handler components and operational condition of air handling components. Discussion: Most of the many potential risk factors assessed here had not been investigated previously, and associations found with single symptom groups may have been by chance, including some that were the reverse of expected. Risk factors newly identified in these analyses that deserve attention include outdoor air intakes less than 60 m above the ground (which were correlated with higher levels of some outdoor vehicle-emitted pollutants), poorly maintained humidification systems, and lack of scheduled inspection for HVAC systems. Infrequent cleaning of cooling coils and drain pans were associated with increases in several symptoms in these as well as prior analyses of BASE data. Replication of these findings is needed, using more objective measurements of both exposure and health response. Co...

Indoor thermal factors and symptoms in office workers: findings from the US EPA BASE study

“…Reducing summer cooling to allow temperatures to stay within the thermal comfort guidelines may thus benefit occupant symptoms, and would certainly benefit occupant thermal comfort while also saving energy. less clear associations between symptoms and humidity ratio, but suggesting small reduction in one or more symptoms with higher moderate humidities in winter. [Note, however, that prior analyses of the BASE data showed increased symptoms associated with the presence of badly maintained humidification systems, which included 40% of the humidification systems studied (Mendell et al., 2008)].…”

“…less clear associations between symptoms and humidity ratio, but suggesting small reduction in one or more symptoms with higher moderate humidities in winter. [Note, however, that prior analyses of the BASE data showed increased symptoms associated with the presence of badly maintained humidification systems, which included 40% of the humidification systems studied (Mendell et al., 2008)].…”

Assessment of Overheating Risk in Gynaecology Scanning Rooms during Near-Heatwave Conditions: A Case Study of the Royal Berkshire Hospital in the UK

“…A more permanent RBH specific solution would be to build air conditioning units into each scanning room, as they are effective at maintaining constant cooler temperatures. With traditional air-conditioning units, a maintenance plan, and a suitable design are essential to ensure that the units themselves are not an infection source due to mould build-up [47,48] and that waste heat is suitably vented away. Good practice in the maintenance and repair of existing energy services is relatively low cost and has an important role to play in improving the resilience of buildings [25].…”

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“…Importantly, whether occupants would operate the IECs for energy saving was not only determined by occupants' willingness, but also by their access to IECs; for instance, our results show that 27.8% of Brazilian and 17.2% of Chinese employees would open or close the windows to save energy, but only 2.0% of US employees would do so. One possible reason is that window controls in the US are more likely to be automated than in other countries, such as China and Brazil [74]; therefore, the US occupants might not be able to close or open windows whether they want to or not.…”