DISPERSION OF AUTOMOTIVE ALTERNATIVE FUEL VAPORS WITHIN A RESIDENCE AND ITS ATTACHED GARAGE

A study was undertaken to investigate the use of mass balance modeling techniques to predict air pollution concentrations in residential set tings where the source is evaporative emissions of alternative fuels e mitted in the attached garage. Field study measurements of the spatial and temporal distribution of evaporative emissions in an attached gar age were used to conduct this investigation, In this field study, know n quantities of methanol were allowed to evaporate in the garage. Meth anol concentrations were then measured and simulated in the garage. Be cause chemical and physical properties of this contaminant are clearly understood, if was possible to simulate the concentrations inside the remainder oi the house. A multi-zonal mass balance model (CONTAM88) w as used to predict the across-residence spatial and temporal distribut ion of concentrations of evaporative emissions from a methanol source inside the attached garage. The model's input data include physical ch aracteristics of the house; parameters characterizing the leakiness of the house; heat, ventilation and air-conditioning system characterist ics; fixed airflow data from vent registers; on-site meteorological me asurements; and information on the contaminant source. Before using th e model to simulate methanol dispersions, the model's performance was tested. Sulfur hexafluoride (SF6) measurements were taken throughout t he residence and garage. The model tvas used to predict interzonal air flow rates and SF6 concentration distributions within the garage and t he house, as well as to investigate the well-mixed zone assumption for the garage. Modeling results show that predicted garage SF6 concentra tions agreed reasonably well with the measured concentrations under mi xed conditions, but the model underpredicted the SF6 concentrations wi thin rooms of the house ih hare mixing was probably incomplete. Methan ol simulation results showed that the model underpredicted by approxim ately 15 percent the garage methanol concentration after methanal emis sions stopped. This study found that evaporative emissions in an attac hed garage have a tendency to infiltrate the house, with rooms adjacen t to the garage showing the highest levels of methanol concentrations. Thus automotive evaporative Emissions may represent a source of indoo r pollution and human exposure in a residential attached garage and al so in other critical locations of the residence.