The Gun, Sword, and Explosive Control Law distinguishes and controls the kind of the gun, which is usually called the gas gun, with the name of the spray.
There is a type of air soft gun, whose propellant is boosted not by the force of the compressed air but by the gas pressure, among the air rifles for hunting, and the law named it the gas gun. Since this gas gun was not generalized, it is just rarely known. In conclusion, as for the gas gun, the defense spray(for the guard, the crime prevention, the public peace) is called the gas gun, as the peppery gas is jetted from it.
If the drugs of the spray is kept for a long time after being made, in powder drugs case, the powder can be congealed within the drug container, and liquid drugs case, the liquid is evaporated within the drug container or dried and stuck to the spray nozzle so that it is not jetted.
In general, the period of validity of the powder drug is estimated about 20-24 months from the date of manufacture, and the period of validity of the liquid drug is estimated about 15-18 months from the date of manufacture. Therefore, the drug container of the spray should be replaced periodically so that the gas gun can keep its performance when jetting in time of emergency.