Achemical that causes a sudden almost instantaneous release of pressure has and heat when subjected to sudden shock pressure or high temperatures best describes which type of dot hazardous materials classification

A hazardous chemical instantly discharging gas, pressure, and heat when subjected to pressure, heat, or high temperature is categorized under hazard class I explosives by the Department of Transportation.  

These are the explosives that possess the tendency to briskly detonate or conflagrate as an outcome of the chemical reaction. The explosives possess the tendency of generating pressures, temperatures, and speeds as leading to catastrophic destruction via force and/or of generating otherwise hazardous concentrations of light, heat, gas, sound, or smoke, all this resulting due to chemical reactions.  

gas

explanation:

smoke is the matter of a gas