Why is it illegal to operate a torch with an acetylene pressure greater than 15psi?

Operating a torch with acetylene at a pressure greater than 15 psi is illegal primarily because acetylene becomes unstable and can pose a significant risk of explosion at higher pressures. Acetylene is a highly flammable gas, and when pressurized beyond this limit, its molecular structure can lead to a hazardous situation where the gas may decompose explosively. This instability can create dangerous conditions, making it critical to adhere to safety guidelines that limit the pressure to ensure safe operation.

While other aspects, such as control difficulties and gas leakage, may be concerns at higher pressures, the fundamental reason for this regulation is the inherent instability of acetylene above 15 psi, which directly relates to safety and the prevention of potentially catastrophic incidents.