COMPARISON OF INDOOR AND OUTDOOR CONCENTRATIONS OF ACID GASES, AMMONIA AND THEIR ASSOCIATED SALTS

The concentrations of ammonia and acid gases inscluding HCl, HNO3 and SO2 as well as their particulate salts were measured both inside and outside the buildings of the University of Essex, U.K., in summer, using diffusion denuder and filter pack samplers. Indoor and outdoor concentration relationships, in terms of the I/O ratios were 0.48 for HCl, 0.22 for HNO3 and SO2, 10.7 for NH3. The average I/O ratios of their particulate salts were 0.52 for Cl−,0.43 for NO3−,0.81 for SO42− and 0.96 for NH4+, respectively. The observed results showed that indoor concentrations correlate well with those outdoors, except for NH3. The concentrations of NH3 indoors were 3.5–21 times higher than those outdoors during the sampling period, indicating that for those pollutants with strong indoor sources there is little correlation between indoors and outdoors. Comparing the dissociation behaviour of volatile ammonium salts in the indoor and outdoor atmosphere, the concentration products indoors were rather lower than the theory predicts. At temperatures above ca. 5°C the outdoor concentration products of NH3 and HNO3 were in a good agreement with the theory, while those of NH3 and HCl were a little lower than the predictions in the same observational period. © 1990 Publications Division Selper Ltd.