The AAT gas hood with the diameters of 1200 - 3000 mm is a cover on the roof of the digester. It is used as an access and removal opening during maintenance work and offers a compact platform for the installation of gas components.

The various flanges on the gas hood are used to fit the following component parts: Gas dome, foam detector, hydraulic over - and underpressure safety device, view port,gas pressure measurement and overfill switch.

The gas dome is the collection point for draining gas from the digester. An integrated water spraying device and a pressure indicator are available as an optional feature.

The hydraulic over - and underpressure safety device secures the digester against impermissible overpressures or underpressures. It has been fitted with an internal, gas-tight,self-regulating water feed.