Fuel gas connections are left hand thread- O2 is right hand. That is on the COUPLER. The pipe connections to the regulators are all right hand thread.. It would be possible to connect a propane regulator to an oxy tank using the oxy tank connector but it would be VERY DANGEWROUS. connecting pressurized oxygen to a regulator with NY flamible gas or oil in it can resulkt in the regulator detonating.