Smog Chambers

Overview

The PSI Simulation Chambers for Atmospheric Chemistry (PSI-SCAC) are a series of medium sized indoor atmospheric simulation chambers. They are a tool to investigate chemical and physical processes related to air pollution under controlled conditions. We perform studies on oxidation mechanisms of gaseous pollutants, particle nucleation and secondary organic aerosol formation and aging. Specific projects and questions addressed so far and at present include:

• Investigation of oligomer formation in SOA
• Determination of SOA yields from various precursor compounds
• Intercomparison of instruments
• Investigation of composition, gas/particle partitioning and volatility of SOA
• Evaluation of photochemical mechanisms
• Investigation of SOA formation from diesel, wood burning and other anthropogenic emission sources
• Investigation of condensed phase processes and their impacts on physical properties of SOA.

Technical Description

There are two chambers at PSI. One larger chamber is a 27-m3 (3×3×3 m) flexible bag made of 125 μm Teflon® fluorocarbon film (FEP), which must maintain a constant volume. The bag is suspended in a temperature controlled wooden enclosure having dimension 4×5×4 m (L×W×H). Temperature can be stabilized at room temperature within the range of 17 to 25 °C, and can be illuminated with a bank of 80 black lights (λ ~ 350 nm) to initiate photochemistry. Sampling manifolds (inlet and outlet) made of stainless steel and Teflon® allow for easy installation of additional inputs and sampling lines.The smaller “cool” chamber is ~9m³ (2x2x2.25 m) flexible chamber also made with a Teflon® fluorocarbon film. The chamber is installed in a temperature controlled shipping container that maintains a temperature (±1 °C) within a range of -10 – 30°C, and also possesses a bank a black lights (λ ~ 350 nm) to initiate photochemistry. The chamber is suspended on rails that allow it to expand or contract as the volume is sampled from the bag. Due to the limited space in the “cool chamber” there is availability to setup some instrumentation directly next to the chamber, but they are required to operate at the chamber temperature (-10 – 30 °C). Additional sampling lines extend the chamber sampling to two additional containers (~3m sampling lines), one designed for gas-phase measurements and the other for aerosol measurements.

For both chambers, purified air is supplied by an AADCO (737-250 series, AADCO Instruments, Inc., USA) pure air generation system. Gaseous components (NO, NO2, gaseous organic compounds) can be delivered to the smog chamber. An ozone generator can provide ozone levels from ppb to ppm concentrations in the chamber. The chamber can be humidified with ultrapure water up to 80 %RH. A particle generation system is available for seed particle experiments.

The smog chamber is equipped with a fixed set of instruments which are regularly operated. Additionally, there are many special state of the art instruments of our own, which are available for specific measurement campaigns.The “cool” chamber is situated next to our combustion emissions platform which allows for the investigation of emissions from a host of different sources, including: residential wood stoves, residential coal stoves, automotive emissions, as well as any open burning emissions (e.g. straw, wood, cow dung, etc…).

For a detailed description see:

Transnational Access

Our smog chambers are partner of the “Infrastructure” program EUROCHAMP-2020 (Integration of European Simulation Chambers for Investigating Atmospheric Processes). This program supports researchers accessing state-of-the-art smog chamber facilities in Europe including ours. EUROCHAMP-2020 offers opportunities to researchers to bring their instruments and expertise to various simulation chambers for measurement campaigns and instrument testing. Details on this "Trans National Access" program can be found here.

Publications

More than 80 papers have been published from smog chamber experiments: see Publication list