Characterization of an indoor environmental chamber and identification of C1–C4 OVOCs during isoprene ozonolysis

Abstract

An environmental chamber was built up and characterized at The Hong Kong Polytechnic University. The chamber consists of a 6 m3 poly tetrafluoroethylene-co-perfluoropropyl vinyl ether Teflon film reactor inside a stainless-steel enclosure stocked with a series of online gas-phase and aerosol-phase analytical instruments. Temperature and relative humidity are controllable and can be set to a range of 10–40 ± 1°C and 5–85%, ± 3%, respectively. An air purification system provides zero air for the chamber with concentrations of total volatile organic compounds < 1 ppb, NOX and O3 < 1 ppb and particles concentration < 102 particles·cm−3. Characterization experiments were performed under dry conditions (relative humidity< 5%) and ambient temperature (25°C). Average wall loss rates of O3 and NO2 were observed as 2.92 × 10−6 s−1 and 9.3 × 10−4 s−1 respectively, and the particle wall loss rate was 0.27 h−1. Dark ozonolysis of isoprene was studied using this chamber and the production of C1–C4 oxygenated volatile organic compounds such as formaldehyde, methacrolein and methyl vinyl ketone (MVK) was identified using proton-transfer-reaction time-of-flight mass spectrometry. Results of experiments indicate that this new facility can be used to investigate and simulate the gaseous chemistry and secondary aerosol formation.