Why Do My Allergies Act Up When the Furnace Comes On?

There is a very good reason for this. You are not imagining this. It is not because the furnace is drying out the air.

Allergy problems and heater operating. Furnace allergy problem. Heating system causes bad allergies.

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There is a Very Common Misconception About Furnaces Drying out the Air.Coarsegold, Oakhurst, Bass Lake. Madera County Home Furnace repair

Furnaces have no ability to dry out the air during the winter months when they are running. It is actually quite the opposite. When furnace heat the air in your home the air's ability to hold and maintain moisture actually increases. Any moisture on the surfaces in the home, including your skin will then give off moisture to the air. Moist always goes to dry. This is the reason that when the furnace is running the air seems drier when it really contains more moisture. An air conditioner removes moisture from the air.

You Probably Still Don't Believe Me

Ask yourself this question. If your furnace is removing moisture from the air that you breathe in your home where is the moisture going? Is there a drain from your furnace to the sewer or outside? Some furnaces (not evaporator coils) do have drains. They are condensing furnaces and range above 90% AFUE. One of the products of natural gas combustion is water. This water is being introduced to burners by the natural gas and must be drained off, but this isn't the air that you breathe. This air is separated by a heat exchanger from your household air.

Why Do Allergies Get Worse When the Heat is Turned Up?Allergy problems and heater operating. Furnace allergy problem. Heating system causes bad allergies.

Allergies get worse when you turn your furnace on for the following reasons:

Dirty Blower wheel
Dirty Filter
Dirty Heat Exchanger
Dirty Ducting
Poorly Sealed Ducting

The Dirty Parts

Furnaces seems to gather all the dust, dirt, debris and dead human skin floating in the air of home and act like a magnet sticking them to the inside of the system. A dirty filter gets packed with this stuff. The packing of the air filter restricts airflow and the smaller open parts of the filter where air can pass through increase in velocity. This increase in velocity pulls some of those dirty pieces through the filter sticking to the motor assembly, heat exchanger, ducting and some of it passes through the entire system landing in your bodies filtration system, your sinuses and lungs where the irritation bears its ugly head in the form of allergies.

It is an Allergy Spreading Machine

It is important to note that the furnace and ducting of your home is not contributing to the dust, dirt and allergies symptoms. They are merely holding spots and relocation avenues for the irritating allergens to inhabit.

The Real ProblemOn time heater service furnace service

The real problem with allergy control and your heating system comes into play with a really good filter and a real well sealed ducting system. Each one by itself will do little to nothing, but combined they can make a very large difference. When ducting is outside the environmental envelope in the home, attic or crawlspace, it often leaks. Every system leaks a little bit and systems older than about 10 years leak a lot. When the furnace is turned on the ducting is pressurized. As this pressurized air escapes into the attic or crawl space the home starts to develop a vacuum. The home cannot sustain a vacuum and the air pressure from inside the home to the outside of the home will become equalized.

Equalized Air Pressure

The way that the home equalizes the air pressure is by sucking air into the home through every crack and crevice, sewer vent, stove hood, water heater vent, plumbing penetration and electrical penetration. The air will even come right through the drywall in the home. This means that if your ducting system is leaking 100 cubic feet of air per minute (about 5% of the average 100,000 Btu furnace) your home is being infiltrated with contaminated air at a rate of 100 cubic per minute.Furnace tune up. Disocunt heating repair

No Wonder the Furnace Makes You Sneeze

Please, stop blaming your furnace for allergy problems and start having a better allergy free winter this year by giving us a call and finding out just how affordable we can make your indoor air comfort.


With one simple Tune-Up, you are able to get more comfort, lower your energy cost and actually reduce the risk of future repairs. The number one cause of system failure is dirt! Don't let a dirty un-tuned system cost you money out of your pocket!