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Furnace Filters 101

You’ve probably heard that you should replace the air filter in your furnace every month. The reason is simple: Your furnace filter removes particles such as dust, mold, pollen, viruses and bacteria from the air in your home and prevents them from damaging your system’s fan and heating coils. A dirty filter impedes the flow of air to your furnace, which makes it work harder to keep you comfortable, increases your energy bills and shortens the life of your unit — all while doing little to improve your home’s air quality.

How to replace your filter
Air filters are easy to replace. The filter is usually located in the blower compartment between the cold air return and the furnace itself. Simply lift out the old filter and slide in the new one with the arrows on the filter frame pointing toward the furnace.

Choosing a filter for your furnace
Filters are given a rating on the minimum efficiency reporting value, or MERV, scale. This scale measures how effective the filter is at removing particles between 0.3 and 10 microns in size; higher MERV ratings translate to smaller particles filtered from the air.

  • MERV 1-4 filters are very inexpensive and remove only particles larger than 10 microns in size. They do little to improve the quality of the air in your home.
  • MERV 5-8 filters trap particles between 3 and 10 microns in size and are ideal for typical residential applications.
  • MERV 9-12 filters trap particles between 1 and 10 microns in size and can help reduce symptoms for those who suffer from allergies and asthma.
  • MERV 13-16 filters trap particles between 0.3 and 10 microns and are generally only used in commercial buildings and hospitals.

Not all furnaces are designed to accommodate filters with higher MERV values, whose thicker design may impede airflow and damage your system. Before upgrading your filter, check the specs of your furnace or contact an HVAC professional for advice.

For more expert advice about air filters, please contact us at Arpi’s Industries, offering home comfort solutions to Calgary for 49 years. We’re always glad to help.

Our goal is to help educate our customers in Calgary, Alberta about energy and home comfort issues (specific to HVAC systems). For more information about furnace filters and other HVAC topics, download our free Home Comfort Resource guide.

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