Furnace Filter Buying Guide

Understanding Furnace Filters

Change your furnace filter every 3 months In general, furnace filters clean dust, dirt, and debris from the air stream that passes through an HVAC system. Keeping such particles out of the furnace improves air quality and protects the inside of the furnace. Allergen reduction filters, such as those we sell here at achoo! ALLERGY, include the added benefit of filtering allergen particles from the air. However, if not used properly, a furnace filter will actually hinder the passage of air, or it can facilitate the introduction of dust and other allergens into your home environment. To avoid this, it's important to change your filter regularly if it's a disposable kind, or clean it if it's permanent. When used to combat allergies, a furnace filter should be used as part of an overall strategy to minimize the allergens in your home.

Types of Furnace Filters

Electrostatic - Often, electrostatic filters are permanent, washable filters that carry an electronic charge that attracts particles much like a magnet. The Newtron Contractor's Choice Permanent Air Filter and the Newtron Original Permanent Air Filter are both such permanent, washable filters. All three Filtrete filters that we offer - the Advanced Allergen, the Ultra Allergen Reduction, and the Micro Allergen - feature electrostatic filters to attract and capture particles.

Pleated - The pleats in pleated furnace filters give the furnace filters more media, or surface area, where particles can be captured. AllergyZone Furnace Filters are pleated electrostatically charged filters. Filtrete's 4" Media Furnace Filters are similarly both pleated and electrostatic; Filtrete's 4" Media filter, however, because of its size, offers more surface area for capturing particles.

HEPA - Although HEPA filters are the gold standard when it comes to filters in air purifiers and vacuum cleaners, they create too much air flow resistance when it comes to furnace filters. We do not carry any HEPA furnace filters.

Activated Carbon - An activated carbon component in a furnace filter enables it to absorb chemicals, fumes, and odors as air passes through your HVAC system. SafeHome Duo Furnace Filters and the SafeHome System Air Return Filters both feature an activated carbon blend to filter out not only allergens, but hazardous chemicals as well, including formaldehyde, ozone, and VOCs.

Changing Furnace Filters

Each of our filters comes with recommendations regarding how often to change them or wash them. In general, disposable furnace filters should be changed once every three months. However, during the winter and summer months when your HVAC system is running often, you may need to change filters more frequently. Similarly, if there's a condition that would make the filters become saturated faster than usual (such as open windows during pollen season, or several pets in the household), you will need to change your filters more often.

To learn more about changing your filter, see When's the Last Time You Changed Your Furnace Filter?

Furnace Filter Sizing

Custom Furnace Filters There's a wide range of furnace filter slot sizes, and most furnace filters come in a wide selection. In addition, SafeHome Duo Filters and the SafeHome System Air Return Filters, as well as the AllergyZone, Newtron Contractor's Choice, and Newtron Original Permanent Air Filters, are all available in custom sizes.

Furnace Filters MERV

MERV is the acronym for Minimum Efficiency Reporting Value. MERV is used to compare one furnace filter's efficiency to another's. When a furnace filter states a MERV, it usually refers to the E3 portion of MERV, which reports a filter's success in capturing larger particles between 3 and 10 microns. Although this is a useful rating to compare filters, it's important to realize that most particles you are interested in capturing are going to be much smaller than this.

The tradeoff between high MERV ratings and efficiency is that sometimes a high MERV can lessen the airflow of your HVAC system. This is especially true with the SafeHome Furnace Filters, and this is the reason the manufacturer suggests a MERV 7 filter for use in conjunction with the SafeHome System Annual Packs (MERV 7 is what they come with), and integrates a MERV 8 filter in the SafeHome Duo. With the SafeHome filters, since they are designed specifically to remove chemicals as well as allergens from the air, it's necessary for airflow to be as unhindered as possible.

That said, when allergen reduction is the primary goal, a high MERV is generally desirable. Filtrete Furnace Filters have impressive MERV ratings: The Micro Allergen, Ultra Allergen Reduction, and Advanced Allergen filters all have MERVs of 11. The AllergyZone Furnace Filter has a MERV of 12.

What is MPR?

MPR is a term used by 3M and stands for Microparticle Performance Rating. It is actually the E1 part of the MERV rating, and measures how efficient an air filter is at capturing particles between 0.3 and 1 micron in size, which make up 99% of the air's particulate matter. Smoke, bacteria, and smog particles fall within this size range, so if filtering these out of the air is important to you, MPR is a good standard to examine. MPR is used to compare furnace filters to one another, and cannot accurately predict how a furnace filter will actually perform in your particular home environment. However, comparing MPRs is a good way to see the differences in efficiency between Filtrete furnace filters. The higher the MPR, the more efficient the filter is at capturing these small particles. For instance, the Micro Allergen Filter has an MPR of 1000, the Filtrete Ultra Allergen Reduction Filter has an MPR of 1250, and the Advanced Allergen Filter has an MPR of 1500. The Filtrete 4" Media Filter has an MPR of 1550, and is the most effective Filtrete furnace filter for those whose HVAC systems can accommodate 4" media.