The York portable Thermal Desorption-Gas Chromatograph-Mass Spectrometer (GCMS) fitted on board the FAAM BAe-146 aircraft is an Agilent 6850 GC- 5975 MS with a Markes International TT24-7 thermal desorption unit. The output includes mixing ratios of a wide range of volatile organic compounds (VOCs), including halomethanes and hydrocarbons.

The sampling frequency is approximately 5 min and every valid sample will be part of the dataset; no averaging done.

Air samples are drawn from the main sampling manifold of the aircraft via a metal bellows pump. The instrument comprises a water removal system through which the air sample stream passes before entering the thermal desorption unit that is coupled to the GC-MS.
The Mass Spectrometer can be run in scan or selected ion monitoring mode depending on the focus of the campaign and species and on required sensitivity.

The instrument is calibrated regularly using a mixed gas standard that varies depending on the requirements of the campaign