Capturing and measuring organic solvent in discharging air

The method of capturing organic solvents, with a boiling point of less than 250 deg C, from effluent air, comprises passing through a ring-shaped bed of absorbent active carbon granules. The bed may be heated when required by electrical current delivered by a transformer. When the bed has reached capacity, the effluent air inlet to the bed is shut off, and fresh air pumped through the bed while it is electrically heated and solvent desorbed. The concentration of solvent in the discharging air is measured, and this value used to control the temperature in the bed in proportion to the concentration; the discharging solvent concentration is measured by a flame ionisation detector; and the maximum temperature of the active carbon bed is pre-selected and adjustable.