When a model with a Gas Mask is forced to take a Toughness test from any weapon source in Warhammer: Skaven, they get a +2 bonus for these tests.
Source: Warhammer Armies Project: Unofficial 9th Edition
When a model with a Gas Mask is forced to take a Toughness test from any weapon source in Warhammer: Skaven, they get a +2 bonus for these tests.