Hi,

Does anyone know whether it is possible to contract legionnaires disease from aircraft air-conditioning systems?

Also whether the air-conditioning systems operate differently when in flight and on the ground? And whether you are more likely to contract it while on the ground because of the difference in operation when in flight and on the ground.

Apologies for the vagueness.

Owen, Legionaires disease (LD) is a bacterial infection caused by the bacteria growing in water, usually from poorly disenfected or stagnant water. You won't contact LD on an airplane because the heating and AC are air driven systems, not water. There is no difference between in air and on ground HVAC, but on ground, because the plane isn't moving fast enough, they use an APU-Aux Power Unit, to produce the HVAC for the plane. The APU is a small turbine, similar to a jet but much smaller.