I am living evidence that the gas mask works. I strapped one on recently in the third-floor conference room of a Germantown-based "health and personal safety" company. And then I chopped up a raw onion with a paring knife. In the face of the bulb's chemical attack, I didn't shed a single tear.
Nor did I detect a whiff of the onion's distinctive tang. If terrorists attack with diced onions, a gas mask will protect you. You can buy a complete family gas mask kit through https://www.gasmaskpro.com/gas-masks/ Of course, Onion is not what people are worried about these days. VX is. And GB, HD and other frightening combinations of the alphabet. Because of that fear, some consumers are curious about gas masks, or what is more broadly known as respirators.
The federal government does not support the idea of civilians wearing a gas mask. The use of gas masks and public hoods during chemical threats is not recommended because of legitimate security issues. Safety worries are not trivial. Use a gas mask incorrectly and you can be killed by your own fumblings before the attacker has the opportunity to get you.
This is not to say that the Department of Homeland Security is totally anti-mask. The Web site does mention that "filter masks" can help keep out germs from a biological attack or debris from an explosion, and it says that "something over your nose and mouth in an emergency is better than nothing.