Never ever connect a torch to acetylene and oxygen tanks without installing a set of recall arrestors in the hoses at the regulators. Without these safety gadgets, it is possible a flash could take place within the tube, and eventually follow back right into the tanks, creating an explosion. This would certainly be an extremely rare incident, however recall arrestors will make it a "never" incident. Check shutoffs are only a first line of defense and may not eventually stop a flashback. Just the recall 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.