The Atmospheric Chemistry Simulation Chambers at PSI (PACS) are an ACTRIS-Switzerland exploratory platform. These simulation chambers are laboratory facilities that can be used to perform different types of atmospheric chemistry under controlled conditions and in the presence of a comprehensive suite of instruments. PACS consists of two simulation chambers, a stationary 27 m3chamber (air-conditioned at 15 to 30 °C), and a stationary 9 m3 cool chamber (air-conditioned between -10 to 30 °C). 

The stationary big chamber has the advantage of a large air volume, which is important when many instruments sample for long times, such as for inter-comparison purposes. The cool chamber is able to simulate secondary organic aerosol (SOA) formation at temperatures as low -10°C, which is especially relevant for wood burning emissions, which typically occur at low temperatures. 

The PACS facility also has full suite of state of the art instrumentation. Depending on the objectives of the campaign, the chambers can be equipped with the following instruments for gas phase characterization: a proton-transfer reaction time of flight mass spectrometer (PTR-TOF-MS), a chemical ionization atmospheric pressure interface time of flight MS (CI-APi-TOF), as well as the standard NOx and ozone monitors; for NO there is also a high sensitivity instrument (detection limit 5 ppt) available, important for experiments a low NOx conditions.

For the characterization of the particle phase the following instrumentation is available: condensation particle counters with different lower cut-off sizes (3 and 10 nm), a particle size magnifier (PSM for even smaller particles, scanning mobility particle sizers (SMPS) for the size distribution (two different size ranges available with a nano and a standard SMPS), a high resolution time of flight aerosol mass spectrometer (TOF-AMS), extractive electrospray ionization time-of-flight mass spectrometer (EESI-ToF), an instrument for on-line determination or reactive oxygen species (ROS) and peroxides. In addition, a FIGAERO (Filter Inlet for Gas and Aerosols) coupled to a CI-APi-TOF is available for chemical speciation of gas and aerosol components. For black carbon measurements, a single particle soot photometer (SP2) and an aethalometer are available.

The 27 m3 atmospheric simulation chamber of PACS