Never connect a torch to acetylene and oxygen tanks without installing a set of flashback arrestors in the hoses at the regulators. Without these safety devices, it is possible a flash can occur within the hose, and ultimately follow back into the tanks, causing an explosion. This would be an extremely rare occurrence, but flashback arrestors will make it a "never" occurrence. Check valves are only a first line of defense and may not ultimately stop a flashback. Only the flashback arrestors will.
Flashback arrestor set has internal check valves for both oxygen and acetylene
Standard -InchB-Inch fittings for 9/16 -18 threads,B size.
Attach at the regulator.
NOTE: The acetylene arrestor in this set can also be used for Propane or Mapp gas.