Listen for a hissing sound, like air being slowly let out of a balloon, which may indicate a leak. However, be aware that a leaking furnace may be silent.
Get on your hands and knees and smell the air closest to the floor, as the weight of propane causes it to circulate near the ground, according to Eastern Propane. If you detect a rotten egg smell, it may be leaking fuel, as additives in propane give it a sulfurous stench to make it noticeable.
Perform a quick visual inspection of the area surrounding your Miller Furnace, checking for anything that may be responsible for the smell. The rotten stench of petrol could be that of a dead animal decaying near the furnace.
Open windows, allowing fresh air to circulate and help break up fuel fumes. Do not light a match or turn on any appliances, as they may create a spark and cause a fire. Turn off any gas-powered appliances and extinguish open flames.
Leave the house, taking anyone else at home with you. Phone for emergency assistance but only after completely vacating the premises.