Characterization of a smog chamber for studying formation and physicochemical properties of secondary organic aerosol

An indoor smog chamber facility has been built for carrying out secondary organic aerosol (SOA) formation and for studying physicochemical properties of SOA. This facility comprises of ~7 m³ FEP Teflon reactor placed in temperature controlled room coupled with instruments for gas and particle phase data. Detailed characterization experiments have been presented describing control of reactor temperature, relative humidity (RH), effective mixing time, wall loss rates of gases and particles, light source, and air purification. This chamber showed a wide range of temperature control with acceptable precision (i.e., 18–33 ± 0.5°C). The gas wall loss rates for NO, NO₂, and O₃ were found to be 3.78 × 10⁻⁴ min⁻¹, 4.48 × 10⁻⁵ min⁻¹, and 6.47 × 10⁻⁵ min⁻¹, respectively. NO₂ photolysis rate constant was 0.17 min⁻¹. Particle wall loss constant was found to be 3.96 × 10⁻³ min⁻¹ at D_p = 100 nm. SOA yields of dark α-pinene ozonolysis ranged from 0.025 to 0.378 for α-pinene concentrations from 10 ppb to 100 ppb.