Determination of HONO Concentration and Investigation on Its Formation Mechanism Using a Continuous Measurement System in Indoor Environment of an Apartment

Nitrous acid (HONO) can be produced by heterogenous reactions of nitrogen dioxide on surface materials and direct emission from combustion sources. However, a little is known of indoor HONO levels or the relationship between residential HONO, NO, and concentrations in occupied houses. Therefore, we measured simultaneously NO, , and HONO concentrations in living room of an apartment using continuous analyzers to study the production of HONO (June , 2006). The 4-min average concentrations of indoor NO, , and HONO were 4.3 (range: ), 10.3 (), and 1.8 ppb (), respectively. Peak levels of HONO up to 7.7 ppb and 24-hr averages as high as 1.7 ppb were measured. In agreement with previous studies, indoor HONO concentrations increased during operation of an unvented gas range. Examination of the observed kinetics suggests that the secondary production of indoor HONO, possibly as a result of heterogeneous reactions involving and is associated with $[NO_2]^2[H_2O]\;(r^2