There are some faulty or inefficient furnaces that may be safely allowed to run until your heating repair professionals arrive. They should be able to tell you over the phone if it's still safe to heat your home or business while you wait to have your furnace problems solved. But there are 3 times when you should immediately shut off the furnace before calling for help.
1) When you smell gas.
If your furnace runs on natural or LP gas, there can be leaks in any number of connections or pipes. Pilot and burner jets can be clogged with dust and debris if not cleaned regularly. Your LP tank may be empty. Any of these situations can cause gas to settle dangerously and begin to smell.
As soon as you detect the sour stench of gas, shut off the supply of gas to the furnace and all appliances. If you still smell a strong gas odor, evacuate your home or business, and contact your gas utility and local fire department.
If the smell does decrease after you shut off the gas supply, check your tank pressure, if needed. Then, see if you note any visible places where gas may be leaking. If you can't rapidly locate the source of the gas leak and correct it yourself without creating a hazard, you must immediately contact a furnace repair professional before trying to restart your furnace.
2) When you notice a burning smell.
It's pretty normal to have a slightly acrid, burnt-dust aroma for a few moments after you first turn on your furnace for the cold weather season. Unless your ducts haven't been regularly cleaned, the smell should dissipate quickly and pose no health risk.
If you smell burning rubber, metal or other strong fiery scents when the furnace is running, you must immediately turn it off, remove the cover and filter, and attempt to see if the unit may be catching on fire. Smoke may billow out of ducts in the event of a serious fire. If you suspect the unit is burning and you have no way to extinguish the flames, get loved ones and pets out of the home and call your fire department. If it is safe to do so, turn off your home's main power source before you evacuate.
Fires in electric furnaces can be small and minor, or they can cause your home to burn to the ground. Always have your furnace inspected if you smell any intense burning odors, and don't use it to heat your home until a thorough inspection is complete.
3) When alarms and detectors tell you the air is unsafe.
If you're not burning fries in the kitchen and your fire alarm and carbon monoxide detector batteries are fresh, trust the warnings these devices give you. They are smarter than you are when it comes to detecting how safe the air is in your home or business.
You may not notice when carbon monoxide begins to poison you, so pay attention and heed the beeping and chirping. Turn off any appliance that might be polluting the air in your home. One by one, turn heaters and devices back on until you can determine the source of the problem. If you suspect your furnace is the issue, keep it turned off until you can have it looked at by the pros.
In most jurisdictions, furnace repair professionals must follow the law when it comes to red-tagging, or locking out, your furnace so that you can't use it. They may be required to cap off gas lines and disconnect power sources until furnace repairs are made, or they may be forbidden from red-tagging your furnace at all.
It's better to trust a furnace repair professional like Kendall Plumbing & Heating Company Inc when it comes to the safety of people and of your property. A dangerous furnace or faulty gas line can put an entire building or neighborhood at risk. Listen to the professionals if they strongly encourage you to shut your furnace off until repairs are made and it's safe to turn it on again.