Yes, if you release propane into an enclosed space like a mechanical room and then introduce a spark, it could cause an explosion.
The explosion risk (in a commercial setting) is mitigated by having gas detection sensors and an exhaust fan that runs when the gas detection alarm trips along with horn/strobes at any entrance to the mechanical room and inside the mechanical room.
In a residential setting, I’d only feel safe if the condenser (outdoor unit) used propane with a liquid to liquid heat exchanger and separate glycol loop that runs inside to the air handler coil.
