soldering pipe with mapp gas
If it is copper pipe and was indeed soldered (using a tin-lead alloy or a more modern lead-free solder), then propane should work okay.  However, MAPP (originally methylacetylene-propadiene propane but now stabilized liquefied petroleum gas with propylene) will heat faster and, with a common sense caution, not melt the pipe.  That is, don't heat the pipe until it is yellow hot; red or orange is fine.

If the pipe was brazed with silver solder, which is common in HVAC systems, propane is not enough:  you have to use MAPP to get it hot enough to work.

Propane and MAPP both burn completely.  You need not worry about the exhaust:  in all cases the result is water vapor and carbon dioxide.  Just like when animals exhale.