A series of experiments was conducted in a self-made photochemical smog chamber in order to simulate atmospheric photochemical reactions of propene and NO_x. The effects of both relative humidity (RH) and the initial C₃H₆ to NO_x concentration ([C₃H₆]₀/[NO_x]₀) ratio on the ozone and CO production in the photochemical reactions were mainly investigated in this paper. Results show that the maximum concentrations of ozone and CO, as well as the concentration of reacted propene linearly decrease with increasing RH. The maximum value of incremental reactivity (IR_max) for propene also declines as RH increases. Their relationships with RH are statistically significant. The effects of [C₃H₆]₀/[NO_x]₀ on the maximum ozone concentration show two different trends. When the ratio is within 1.0～3.4, the maximum ozone concentration greatly increases with increasing ratio, whereas for the ratio of 3.7 to 7.4, it gradually decreases as the ratio increases. The comparison between smog-chamber data and results from the propene sub-mechanism of MCMv3.1 is also made in this work.

Key words: smog chamber, photochemical reaction, propene, relative humidity, incremental reactivity