If you’re wondering if meters for detecting chemical agents similar to the ones that the gas company uses to find gas leaks in your home are available, the answer is yes, but you shouldn’t rely on them to keep you safe as they’re limited in scope.
Various companies offer them for industrial gases, cyanide, chlorine, etc., but won’t detect nerve gases or some specialized warfare agents. These meters are usually handheld and look just like the fire department or gas company ones. Many of these are only calibrated to detect one type of gas. The U.S. Army has the Joint Chemical Agent Detector (JCAD) M4A1, which is another handheld unit and pretty bulky. They start at around $2,500, with many in the $7,500 to $10,000 region.