Use of a two-tiered dynamic chamber to investigate indoor air chemistry

A two tiered dynamic chamber was assembled for the purpose of investigating indoor air chemistry. This design consists of a smaller chamber nested inside of a larger one and allows for conditions of temperature, relative humidity, and surfaces types to be carefully controlled. Three series of experiments were conducted investigating different aspects of indoor air chemistry.; The first series of experiments investigated the effects of relative humidity and surface type on nitrous acid (HONO) formation from the reaction of nitrogen dioxide (NO2) with water vapor (H2O). The experimental results show that both surface type and relative humidity play a large role in the production and lifetime of HONO in indoor environments. Synthetic carpet increased the NO2 deposition velocity by nearly an order of magnitude and doubled the peak HONO/NO2 ratio. Vinyl wallpaper was found to act as a sink/source for HONO and the HONO emission rate from the wallpaper was found to be directly proportional to the HONO/NO 2 ratio.; A second series of experiments investigated the production of nitric acid (HNO3) through the reaction of NO2 and ozone (O 3). HNO3 formation was determined by measuring particles formed by its reaction with ammonia (NH3) and was found to be dependent relative humidity. Indoor HNO3 is often considered to be the result of infiltration of ambient air. The results of this work show clearly that indoor sources of HNO3 exist.; A third series of experiments investigated secondary particle formation through the reaction of O3 and limonene. Significant mass concentrations as a result of the limonene-O3 reaction were produced in all of the experiments. The occurrence of this and other indoor sources of fine particles make it seem unlikely that the new NAAQS for PM2.5 will be attained in indoor environments where people obtain a significant fraction of their total particle exposure. In view of the significance of indoor particle sources to overall exposure, long term studies of PM2.5 in personal and indoor air should now be conducted in order to assess the efficacy of the PM2.5 standard in reducing people's overall exposure to fine particles.