Furnace Filter Facts

Furnace Filters and Indoor Air Quality
Poor Indoor Air Quality can cause or aggravate respiratory problems, allergies and asthma. Todayís weather-tight homes trap pollutants inside where everyday household contaminants become increasingly concentrated.

The result, indoor air quality can be up to 50 times more polluted than the air outdoors, jeopardizing the health and vitality of your family.

Controlling the source of various pollutants is the ideal solution, but in most cases it simply isnít possible. Minimizing the sources of pollutants in your home, by changing your furnace and humidifier filters regularly, is the right solution to ensure good Indoor Air Quality.

Indoor air can be 50 times more polluted than outdoor air.
The average person spends more than 80% of their time indoors.
More than 40 million Americans suffer from allergies. One out of six allergy sufferers is affected by fungi and bacteria in home air duct systems.
12 million Americans suffer from asthma.
The Relative humidity of the Sahara Desert is 25%, and 23% for Death Valley. The average heated home has a relative humidity level between 13% and 16%.
Electrostatic and standard throw away furnace filters trap only 15% of the pollutant particles in the air leaving the rest to circulate throughout your home.

Furnace Configurations
A gas furnace is comprised of a heating device as well as an air circulating fan. Depending on which direction the furnace fan blows and how the furnace is installed, describes the unit’s configuration type.
There are three configuration types that furnaces are available in: up-flow, down-flow and horizontal-flow.
Up-Flow Split System (often installed in a basement)
Horizontal-Flow Furnace (usually installed in an attic)
Down-Flow Furnace (often installed in a closet)

Looking at the pictures below and selecting which is most similar to how your furnace is installed will help identify where your furnace filter or air cleaner will be found. In all cases the filter will be found attached to the return air opening.

Identifying the Make & Model
Electronic Air Cleaner
• Found somewhere along the outer perimeter of the air cleaner cabinet, or behind the filter access door.

Media Air Cleaners
• Media filters almost always have the replacement filter part number stamped on their old filter. Failing that, check for the model & make of the air cleaner usually found on the outer perimeter of the cabinet.

• Humidifiers have the model number usually stamped on an identification plate mounted either on the front, side or the bottom of the cabinet.

Standard 1” Disposable Filters
• A 1” filter can be found inside the blower compartment, or more commonly externally mounted on filter rack. Depending on your configuration, that can be on the left, right, top, or bottom of the furnace/air handler. If the filter is in the blower compartment, the filter thickness is likely a nominal size of 1”

Tips: Furnace/air handler makes & models never tell you what filter size or filter type you require. The information above requires that you focus on the manufacturer of the air cleaner, not the furnace/air handler. Parts ordered right the first time save you time and money. Consider your filter dimensions, if the filter is more than 1” thick, you most likely have an air cleaner.

Important: To prevent serious injury, always turn the furnace or air handler power off before attempting the above.

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