0 a device worn over the face to prevent you from breathing in poisonous gases
1 a device a person wears over the face to protect against breathing in poisonous gases
It was discovered that, having a long face, the standard gas mask did not fit me.
Must such a person change his or her gas mask?
Gas mask carriers fall within the scope of the tax.
A gas mask is of no value whatsoever.
It is true that no gas mask will operate in regard to the skin, because there is a certain gas which produces blisters.
We had to wear a gas mask to handle it.
To counter this, people have been issued with a type of gas mask which fits over the mouth and nose.
Both of those are very difficult from behind a gas mask.