While you are home during the winter, you start to notice a strange odor. After realizing that the smell only happens when your gas furnace is running, you suspect you may have a problem. Below are the types of odors you could encounter, as well as their potential causes.
Burnt, Musty Odor
At the beginning of the cold season when you first turn on your furnace, you more than likely will smell a burnt, musty odor. This is caused by the heating up of the dust that has accumulated inside the ducts and unit while it was not being used. After your heater has cycled through a few times, you should no longer smell it.
If you continue to smell the odor after a day, check your filter. When it sits for long periods of time without air circulating through it, dust, cobwebs, and mold will start to gather within its fibers. If you cannot remember the last time you changed it or if it was at the end of last winter, it should be changed before running your heater again.
After examining and changing your filter, you may still detect the musty odor. Try cleaning your air vents to see if that makes a difference. If the problem smell persists, you may want to call an HVAC repairman to take a look at your furnace.
Rancid, Decayed Odor
While trying to determine the cause of the odor coming from your furnace, you may start to think to yourself that it smells as though something died in there. Unfortunately, if you think that because the odor is rancid and smells like decay, there is a good possibility that something did die either in your furnace or ductwork.
When you have open vents on the outside of your home, animals such as birds and squirrels may enter while trying to find a place to roost or nest. If they become stuck in your ducts, they may die and their bodies will start to decay. When your furnace runs, it spreads the smells throughout your house.
If you think you have a dead animal in your HVAC system, open the panel on your furnace and look for signs, such as fur, feathers, or the animal itself. Try taking a broom handle and gently poking it into the vents to see if the carcass becomes dislodged.
If you still cannot find the problem, you will need to call an HVAC professional to investigate and hopefully clean the animal's corpse out of your system. They can then put screens on your outer vents to prevent animal entry in the future.
Strong Gas Odor
If the odor you are smelling is that of natural gas, you want to investigate it immediately. A gas leak presents a serious fire and explosion risk. Also, prolonged exposure to it can have adverse health effects on your and your family's health, such as nausea, fatigue, and passing out. It could even eventually lead to death, if the leak is bad enough.
The simplest cause of a strong gas odor is that the pilot light has gone out. To check it, remove the panel on your furnace and see if it is still lit. If not, follow your furnace's owner's manual for instructions on how to relight it.
However, if your pilot light is lit and you the smell become stronger, you may have a crack in one of your gas lines or in the furnace itself. Open your windows, leave your home, and call your gas company immediately. They can send someone out to inspect your lines and furnace to find out where the odor is coming from.
After finding out what is causing or not causing the odors, you may feel that the problem lies outside your area of expertise. If so, you may want to contact an HVAC contractor such as Cydcom Services to inspect your gas furnace to see if it needs repaired or replaced.