When a furnace is running properly, you shouldn't notice that it's running at all. But if you turn on your furnace and get a nose-full of some unpleasant smell, you're right to be worried. Is your furnace odor something you can fix yourself? Is it something that will go away on its own? Or should you be shutting off your furnace right away?
Dusty or Musty
When your furnace first starts up, you might notice a musty smell. As long as it goes away, this is no big deal; when your furnace isn't in use, it can become dusty, and some of this dust is burned away when you turn your furnace back on. The longer your furnace has been out of use, the more time you should give the odor to go away. But if the smell doesn't go away on its own after a few days, something is wrong.
The first thing to check for this type of odor is whether the filter is dirty or clogged. This is especially likely if you haven't been replacing or cleaning it regularly; checking it monthly is a good idea although it may only need to be replaced every few months. If you pull out the filter and it looks very dirty, try replacing or cleaning it.
If your filter looks clean or replacing or cleaning it doesn't get rid of the smell, it's time to call a contractor. You may have dust and dirt accumulated in your ductwork or even mold growth. A contractor will likely give your unit a thorough cleaning and inspection.
Burning or Electrical
While dust can burn away when a furnace is started up, this is a different smell from that of burning wiring or plastic; this is often called an electrical smell. This type of burning or electrical odor from your furnace is definitely not normal. It may mean that the insulation on wiring is damaged and melting or that motor components are overstressed.
Whatever the cause, if you have an electrical burning odor, you should turn off your furnace and call a contractor to inspect it. Continuing to run your furnace may cause further damage depending on the root of the odor.
Gas or Oil
Because gas leaks are very dangerous, additives are added to make it easy to detect gas in the air. If you smell the familiar sulfur smell of a gas leak, you should shut off your furnace and leave your home immediately. Using a cellphone or a neighbor's phone, call the local fire department or utility company so that the gas line to your home can be shut off. The utility company will likely come to inspect for a leak in your supply line. If the line isn't leaking, you'll need to have a contractor come look at the furnace system to determine where the gas is leaking from.
Oil leaks are not as dangerous as gas leaks and don't require evacuation. However, oil is still flammable, so if you have an oil furnace and can smell oil, shut off your furnace and call a contractor. You likely have a crack somewhere in your furnace that should be repaired as soon as possible.
For more information, contact Bristol Heating & Air Conditioning or a similar company.