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Indoor/Outdoor Ozone in Evaporative Cooler vs Central Air Homes in Utah County

Year: 2023

Presenter Name: Seth Van Roosendaal

Additional Presenters:
Braedon Tarone (
Ozone is known to be higher in the summer months when sunlight, Volatile Organic Compounds (VOCs), and Nitrogen Oxides (NOx) readily react: Sunlight + NOx + VOCs = Ozone. Exposure to ozone in concentrations higher than the Environmental Protection Agency's (EPA) National Ambient Air Quality Standard (NAAQS) of 70 ppb can lead to adverse health effects such as reduced lung capacity, exacerbated chronic obstructive pulmonary disease, asthma, bronchitis or heart disease. Little is known regarding the effects of various residential cooling methods on indoor ozone concentrations. We recruited homes in Utah County that use either central air conditioning (AC) or evaporative coolers (EC) during summer months. Gilian 113 Low Flow samplers were used to sample air over a 24-hour period through coated nitrite filters. Nitrite (NO2) on the filter reacts with any ozone (O3) present to form nitrate (NO3) which can then be measured to obtain an accurate ozone air concentration: NO2 + O3 = NO3 + O2. Two ozone samples were collected at each home with one indoors and one outdoors. Monitors were placed in a main living area of the home away from vents, air intakes, and main entrances. 30 samples were taken inside (n=15) and outside (n=15) AC homes. Additionally, 14 samples were taken inside (n=7) and outside (n=7) EC homes. Samples were analyzed at SGS Galson Labs according to OSHA Method ID-214 to determine total concentration of ozone on each filter. Mean concentrations outside AC homes were 0.036 ppm. Mean concentrations inside and outside EC homes were 0.020 and 0.034 ppm, respectively. The indoor to outdoor (I/O) ratio of mean concentrations for EC homes was 0.596. Samples taken indoors at AC homes were below the limit of detection (LOD), therefore the I/O ratio for AC homes could not be calculated. Only 1 sample taken inside an AC home contained a concentration above the LOD, which was labeled an outlier and removed. Additionally, data from samples taken outdoors were compared to outdoor ozone concentrations measured at collection sites operated by the Utah Division of Air Quality. Homes provide a protective envelope from exposure to outdoor air pollution. All outdoor ozone concentrations were higher than indoor concentrations, suggesting both AC and EC homes provide this protection. However, our data suggests AC homes provide more protection than EC homes, as samples containing ozone concentrations below the LOD taken from inside AC homes are significantly lower than the calculated mean concentration inside EC homes.
University / Institution: Brigham Young University
Type: Poster
Format: In Person
Presentation #D39
SESSION D (3:30-5:00PM)
Area of Research: Health & Medicine
Faculty Mentor: James Johnston