Ok so a lot of criminal classes have been complaining about mustard gas. So instead of nerfing mustard gas or taking it away we just simply add gas masks the to black market dealer. With mustard gas it is taking away a lot of crims chance to get crime done, because you have like 3 swat/cert members that have more armor pushing you and that alone is hard to fight against, then they start chucking gas and you have nothing to do but run and get shot right away when you clear from gas. Now crims have a better chance with having gas mask in black market dealer.