To dream of a gas mask represents the choice avoid paying attention to how negative or dangerous a situation feels. Positively, it may be a sign that you are confronting a very unpleasant situation head on. Putting up with very unpleasant conditions responsibly.
Negatively, a gas mask may reflect willful blindness. Knowing how dangerous or negative a situation is and doing everything you can to avoid the consequences of it. Filtering out feelings or information you don’t like.