Air Exchange Rate Experiments in a Detached House Using a Continuous Monitor. L. A. Wallace, USEPA, 11568 Woodhollow Ct., Reston VA 22091; and W. R. Ott, Dept. of Statistics, Stanford University, Stanford, CA 94305
Air exchange rates were measured in a detached house in California under a variety of conditions for 80 days over a period of about one year. A continuous monitor (Bruel & Kjaer) tracked the decline of sulfur hexafluoride (SF6) over periods of 16 hours following a 30-minute release at 200 ml/min. The single most important determinant of variation in air exchange rates was opening exterior windows or doors. The effect of opening one window by amounts varying from 1-18 inches was carefully studied in more than a dozen experiments. The effects of opening several windows at once, closing off some rooms in the house, use of air conditioning, and placing the monitor in different rooms were also determined. Evidence was found for a "deep" compartment in the home, most probably consisting of closets, cabinets, furniture interiors, etc., which in this case amounted to approximately 10% of the house volume, and had a typical air exchange rate with the well-mixed portion of the home of about 1.2 h-1. (The typical air exchange rate of the home as a whole was about 0.4 h-1.) Maximum air exchange rates on the order of 12 h-1 were achieved when all doors and windows were opened. The effect of indoor-outdoor temperature differences was determined, but was small compared to the window/door effect.