As stated in your other thread on this subject, there is no reason why any aircrew, in any air force, during WW2 would carry a gas mask as part of normal operational equipment.
However, members of all branches of all of the armed forces, and civilian populations, during WW2, were issued with a gas mask, for use on the ground, in the event of a gas attack. They were a standard part of military equipment issue, just as a boot cleaning kit was. But, like the boot cleaning kit, they would not be carried into the air. There was no reason for them to be, and they would have been of no use whatsoever.