Many homes in the US have attached garages. Of the over 130 million housing units in the US, 83 million have a garage or carport included with the home (2011 American Housing Survey). Studies over the past 25 years have shown that the house-garage interface can be an entry point for pollutants from the garage and vehicles to move into the home. Pollutants of concern include evaporative VOC emissions such as benzene (Furtaw et al. 1993, Mann et al. 2001) from cars, gas-powered appliances and/or lawn mowers, car tailpipe emissions such as carbon monoxide (Graham et al. 1999, Wilber and Klossner 1997), and particulate matter, evaporative emissions from stored solvents and other potentially harmful compounds (Noseworthy and Graham 1999, Fugler et al. 2002, Lansari et al. 1996).
Of significant concern is the possibility of accidental carbon monoxide (CO) poisoning. A significant number of people are killed or injured from exposure to vehicular exhaust each year. Based on the most recent available data from the National Highway Traffic Safety Administration, in 2003 and 2004 there were 294 fatalities and an estimated 4,000 injuries from accidental carbon monoxide poisoning (NHTSA, 2009). Additionally the US Fire Administration statistics show that between 2007 and 2009, about 5% of all fires in homes originated in the garage.
Evaporative emissions in an attached garage have a tendency to infiltrate into the home. In a study by Lansari and colleagues, the rooms next to the garage typically had the highest levels of pollutants (Lansari et al. 1996). In this study, methanol was used to represent evaporative emissions and a model (CONTAM) was used to predict the transport of methanol between the garage and the house.
The infiltration of vehicle emissions into sixteen homes from their attached garages was investigated over two winter seasons in Canada. Results showed that nonmethane hydrocarbon infiltration emissions varied widely with between 9 and 85% of the garage emissions measured in the house (Graham et al. 2004).
Fan depressurization tests of the house-garage (HG) interface in the Canadian study showed that many of the air-leaks from the garage led to the basement; four out of 25 homes studied had more significant leaks into the main floor. The Equivalent Leakage Area (ELA) ranged from 4 – 400 cm2, with an average of 140 cm2, which was 13% of the overall house leakage area (Graham et al. 2004). The HG interface is built as leaky as the rest of the house envelope. The average monitored pressure difference between the house and garage was 0.5 Pa in summer and 1.6 Pa in winter.
These studies show the potential for residential indoor air quality problems in homes that have attached garages. There is a lack of data, however, to understand the parameters likely to lead to problems. Data is also needed to analyze the effectiveness of interventions that can be used in new and existing garages to reduce pollutant infiltration. Luckily, the American Society for Heating, Refrigerating and Air-Conditioning Engineers just funded a study to determine what strategies can be used to keep the pollutants generated in your garage from leaking into your house. Stay tuned, the results should be available in the next couple of years.
References and Other Related literature
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- ASTM (1999). ASTM Guide E1998-99, Standard Guide For Assessing Depressurization-Induced Backdrafting and Spillage From Vented Combustion Appliances. Philadelphia, PA; American Society for Testing and Materials. http://www.astm.org.
- Lansari A, Streicher JJ, Huber AH, Crescenti GH, Zweidinger RB, Duncan JW, Weisel CP, Burton RM (1996). Dispersion of auto- motive alternative fuel vapors within a residence and its attached garage. Indoor Air, 6(2):118–126.
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- Furtaw EJ, Pandian MD, Behar JV (1993). Human exposure in residences to benzene vapors from attached garages. In Proceedings of International Conference on Indoor Air Quality and Climate, Indoor Air, volume 93.
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- Kim AK and Shaw CY (1986), “Seasonal Variation in Airtightness of Two Detached Houses,” Measured Air Leakage of Buildings, ASTMSTP904, H. R. Trechsel and P. L. Lagus, Eds., American Society for Testing and Materials, Philadelphia, pp. 17-32.
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- Wilber MW and Klossner SR (1997). A study of undiagnosed carbon monoxide complaints. In Proceedings of Healthy Buildings/IAQ, volume 97.
- National Highway Traffic Safety Administration (2009). Not-in-traffic surveillance 2007: High- lights. Technical Report DOT HS 811 085: Traffic Safety Facts, Crash Stats, National Highway Traffic Safety Administration, National Center for Statistics and Analysis. www-nrd.nhtsa.dot.gov/Pubs/811085.PDF.
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