Sources of organic acids in indoor air: a field study.

Simultaneous indoor and outdoor measurements of organic acids were made at six residential houses located in a suburban New Jersey area during the summer of 1992. Each house was measured for six days and controlled for ventilation and gas combustion conditions. The study presents the first set of simultaneous measurements of formic and acetic acid in indoor and outdoor air. The concentrations of formic acid were 1.24 +/- 1.17 ppb outdoors and 8.77 +/- 4.67 ppb indoors. The concentrations of acetic acid were 3.05 +/- 3.63 ppb outdoors and 23.97 +/- 16.20 ppb indoors. The higher indoor concentrations indicated the presence of significant indoor sources such as direct emissions and indoor chemical formation. However, the results indicated that organic acids indoors were not likely to be emitted from indoor gas combustion. The study also collected temperature, humidity, ozone, aldehyde, and nitrogen dioxide data, and provided the supporting evidence for indoor chemical reaction pathways leading to organic acid formation.