Dispersion of Automotive Alternative Fuel Vapors within a Residence and Its Attached Garage

Abstract

A study was undertaken to investigate the use of mass balance modeling techniques to predict air pollution concentrations in residential settings where the source is evaporative emissions of alternative fuels emitted in the attached garage. Field study measurements of the spatial and temporal distribution of evaporative emissions in an attached garage were used to conduct this investigation. In this field study, known quantities of methanol were allowed to evaporate in the garage. Methanol concentrations were then measured and simulated in the garage. Because chemical and physical properties of this contaminant are clearly understood, it was possible to simulate the concentrations inside the remainder of the house. A multi‐zonal mass balance model (CONTAM88) was used to predict the across‐residence spatial and temporal distribution of concentrations of evaporative emissions from a methanol source inside the attached garage. The model's input data include physical characteristics of the house; parameters characterizing the leakiness of the house; heat, ventilation and air‐conditioning system characteristics; fixed airflow data from vent registers; on‐site meteorological measurements; and information on the contaminant source. Before using the model to simulate methanol dispersions, the model's performance was tested. Sulfur hexafluoride (SF6) measurements were taken throughout the residence and garage. The model was used to predict interzonal airflow rates and SF6 concentration distributions within the garage and the house, as well as to investigate the well‐mixed zone assumption for the garage. Modeling results show that predicted garage SF6 concentrations agreed reasonably well with the measured concentrations under mixed conditions, but the model underpredicted the SF6 concentrations within rooms of the house where mixing was probably incomplete. Methanol simulation results showed that the model underpredicted by approximately 15 percent the garage methanol concentration after methanol emissions stopped. This study found that evaporative emissions in an attached garage have a tendency to infiltrate the house, with rooms adjacent to the garage showing the highest levels of methanol concentrations. Thus automotive evaporative emissions may represent a source of indoor pollution and human exposure in a residential attached garage and also in other critical locations of the residence.

Relationships of attached garage and home exposures to fuel type and emission levels of garage sources

“…A number of studies have reported vehicles parked in attached garages as an important source of toxic organic compounds inside residences (Hawthorne et al 1986; Thomas et al 1993;Lansari et al 1996;Tsai and Weisel 2000;Mann et al 2001;Graham et al 2004;Dodson et al 2008). In addition to vehicles, people often store gasoline, yard, and garden supplies in garages, which can also be a source of volatile organic compounds (VOC, Batterman et al 2006).…”

The benefits of whole-house in-duct air cleaning in reducing exposures to fine particulate matter of outdoor origin: A modeling analysis

“…CONTAM provides dynamic simulations of inter-zonal airflow, ventilation rates, and concentrations of gaseous and aerosol pollutants. The performance of the model has been evaluated extensively (Lansari et al, 1996;Emmerich and Nabinger, 2000;Emmerich et al, 2003;Howard-Reed et al, 2004. Of particular relevance to our application, Emmerich et al (2003) and Emmerich and Nabinger, (2000) found that modeled average fine particle levels were within 30% of the measured values during a study of air cleaner performance in a single-zone test home.…”

Contribution of Vehicle Emissions from an Attached Garage to Residential Indoor Air Pollution Levels

“…CO emissions in the context of accidental deaths or suicide attempts 1,2 and fuel vapors evaporating from vehicles [3][4][5] were the topics of studies reported at the time. These studies reported on a limited number of measurements, usually a single vehicle in a single garage; tracer studies using sulfur hexafluoride (SF 6 ); or modeling estimates based on assumed conditions of emission rate and house volume.…”