Gas Line

• While being much smaller than a full-sized propane furnace for central heating, a wall-mounted unit still requires its own line to a propane tank located outside the home according to Propane 101, a website created by a group of propane dealers. Flexible metal pipe approved for propane and correctly sized for the fuel capacity of the heater must be used for safe operation. Other metal piping will work, but flexible lines are most common because they bend around wall studs and other obstacles to make installation easier.
  
  

Clearance

• The wall-mounted heater won't damage the drywall or plaster around the unit, but you still need to keep it away from combustible materials. The unit needs to be mounted at least 6 inches above the floor, says Eskabe Heaters, a company in Argentina that manufactures propane wall heaters. The heater also needs to be 6 inches away from any adjacent walls. At least 36 inches of space is needed between the top of the propane heater and the ceiling, since the heat rises and has a greater potential for causing a fire to the material above it.
  
  

Venting

• Most propane wall heaters are designed for installation on an exterior wall due to ventilation requirements. Burning any fuel, including propane, creates carbon monoxide and other fumes that can be harmful if inhaled. Direct vent units install through the wall and the exposed back of the unit vents all fumes, according to Cozy Heaters, a manufacturer of wall-mounted propane heaters in Kentucky. Other models require an approved vent pipe to be run through the wall. This vent pipe can be short and completely horizontal, unlike wood stove vents, which need a long vertical run for correct drafting.
  
  

Sealant

• For the ventilation system to work properly, it must be fully sealed. Heaters that come with vent pipes include a silicon gasket to seal the point where the pipe meets the back of the heater, but you'll need to purchase if you're assembling your own ventilation pipes. The metal mounting plates that anchor the vent pipe on both the exterior and interior sides of the wall must both be sealed with silicon caulk, Eskabe Heaters advises.