In 1986, the United States Congress passed Public Law 99-145 directing the destruction of wartime chemicals stockpiled at eight sites around the country. It is a liquid not a gas.
Mustard agent smells like garlic or mustard.
It is thick like oil at warmer temperatures and freezes at 58.01-degrees Fahrenheit. The mustard agent at CASY is essentially a solid for approximately six months each year. An external action, such as fire or explosion, is required to spread HD in droplet, aerosol, or vapor form. There are no explosives involved. CASY is a highly secured facility.