The effects of evaporative cooling on indoor /outdoor air quality in an arid region

Helmut William Paschold, University of Texas at El Paso


Indoor and outdoor particulate matter concentrations have been measured during 2000 and 2001 to determine the effects of evaporative cooling on ambient air in an evaporative cooler test chamber. The test chamber experiment was conducted to familiarize the experimenters with the instruments and evaporative cooling process; evaluate the impact of evaporative cooling without confounding by household activities such as cooking, cleaning, smoking, etc.; and determine subsequent testing protocol for the task of actual residential monitoring. Measurements of particulate matter were performed with TEOM (Tapered Element Oscillating Microbalance) instruments to provide a larger number of data points for comparison. Based on the experiments performed on two popular models of evaporative coolers, it was found that the evaporative cooler reduces indoor PM10 by approximately 50%, and has a varying reduction effect of between 10 to 40% on PM2.5. These findings are consistent with the predicted outcomes suggested by particulate matter deposition models applied to the evaporative cooler media pad properties. In the summer of 2001, ten residences in the El Paso, Texas region were continuously monitored for indoor and outdoor PM with the TEOMs. Concurrent indoor and outdoor 10-minute averaged PM levels were recorded two days each for PM2.5 and PM10 in an attempt to establish the indoor-outdoor PM correlation for typical west Texas residences equipped with evaporative coolers. In a typical house equipped with evaporative coolers, indoor PM concentrations stabilize in approximately ten minutes. If the ambient PM concentration remains steady, a 10-minute average indoor air sample after the first 10-minute period would contain 99% outdoor air and a one-hour average indoor air sample would actually be represented by 95% of the outdoor air. Nine of the tested houses displayed a strong diurnal pattern of PM10 indoors and outdoors, independent of the possible human activities and other indoor sources at each residence. Consistent with prior regional studies, indoor and outdoor PM 10 concentrations at these houses frequently peaked with strong association with each other in the evening hours between 6 to 9 p.m. In addition, a correlation was observed as indoor and outdoor PM10 peaked after the wind speed and wind gust peaked. Peaks in indoor PM concentrations clearly correlated with documentation of human activities, however, with short duration due to the high ventilation rates of the evaporative coolers. (Abstract shortened by UMI.)

Subject Area

Environmental engineering|Environmental science|Civil engineering

Recommended Citation

Paschold, Helmut William, "The effects of evaporative cooling on indoor /outdoor air quality in an arid region" (2002). ETD Collection for University of Texas, El Paso. AAI3080480.