The Complete Guide to Furnace Filters

Did you know that some filters can even block sneezes from contaminating a room?

Do you feel confident that your furnace filters can block allergens, bacteria, or viruses?

Homeowners need a fundamental understanding of this topic to provide a clean and safe home for their loved ones. If you don’t take the time to find the best furnace filters for your situation, you can put yourself and your family at risk.

Don’t procrastinate any longer, and take the time to read this complete guide to furnace filters.

Furnace Filter Terms You Need to Know

Before diving into the specifics, it’s critical to familiarize yourself with a few essential terms. Your furnace filters education isn’t complete without reviewing this information.

Understanding these ratings before choosing a company to service your HVAC system can help you decide which local contractor to hire.

Minimum Efficiency Reporting Value (MERV)

Minimum efficiency reporting value (MERV) measures the effectiveness of air filters.

The scale ranges from 1 to 16. The higher the rating, the fewer contaminants or dust particles can get through. Most good quality filters achieve a MERV rating of at least 10.

High-Efficiency Particulate Air (HEPA)

A HEPA filter stops a minimum of 99.5% of dust and other contaminants from entering your home. This certification started in 1983, but these filters go back to World War II and the Manhattan Project. Scientists created the first HEPA filter to catch radioactive particles from nuclear blasts.

Microparticle Performing Rating (MPR)

3M uses what they call a Microparticle Performing Rating (MPR). You’re going to find plenty of 3M products in the wild, so you need to know their company standard.

This rating measures a filter’s ability to capture airborne contaminants smaller than 1 micron. Look for filters that have an MPR rating between 1,500 and 1,900.

Filter Performance Rating (FPR)

Home Depot also provides a company rating for furnace air filters. They use a simple 1 to 10 scale and, as you would assume, the higher the number, the better performance you can expect.

Understanding MERV Ratings for Filters

The MERV rating tells you what size particles your filters can capture and how much they can remove. It’s crucial to understand what each rating means for your home. The Environmental Protection Agency (EPA) even has a guide for MERV ratings on its website.

MERV 1-4

As you would assume with the lower number, this MERV rating represents base-level protection. These filters only catch large particles like the following:

  • Dust mites
  • Carpet fibers
  • Sanding dust
  • Spray paint dust

You’re more likely to find these filters in window air conditioning units. This rating isn’t an appropriate fit for furnaces.

MERV 5-8

It’s common to find a MERV 8 filter in your home. That rating captures 80 to 90 percent of particles ranging from 10 microns to 3.

You could consider a MERV 5 to 7 filter, but most experts agree on eight as a minimum. You have enough protection here to capture the following:

  • Hair spray
  • Mold spores
  • Dusting aids
  • Cement dust
  • Fabric protectors

MERV 9 – 12

These filters capture between 90 and 95 percent of particles that range from 3 microns to 1. You’ll find these used in hospitals, but they don’t quite reach the filtration necessary for a surgery room.

If you choose a MERV 9 to 12 air filter, you have enough protection to capture:

  • Lead dust
  • Milled flour
  • Car emissions
  • Welding fumes
  • Humidifier dust

MERV 13-16

These air filters often find their use in hospitals, and they’re at least 98 percent effective. You don’t see these used in residential settings often because it’s more efficient than most furnaces need.

A MERV 13 to 16 rating gives you protection from cigarette smoke, all bacteria, and even sneezes.

MERV 17-20

You only find air filters with this MERV rating in places like clean rooms. A MERV 17 to 20 rating means a filter can capture bacteria or viruses right out of the air.

What Type of Filter Should You Choose?

Everything depends on your situation, so consider the following factors:

  • Do you have pets?
  • Do you or loved ones have allergies?
  • Do you live near an active construction site?
  • Do you or loved ones have a sensitivity to air pollutants?

Even if you have hypoallergenic pets, your air filter needs to do more work to keep harmful contaminants out of your home. Find a filter that’s rated to handle removing pet hair and dander.

The American College of Allergy, Asthma & Immunology recommends the following:

  • For a single room, find a HEPA filter that has a clean air delivery rate (CADR) that will work for the square footage
  • For a “whole house” filtration system, use filters with a MERV rating between 11 and 13

How to Change Furnace Filters

After you’ve changed a filter for the first time, you’ll understand what you need to do in the future. If you follow three simple steps, you won’t need to sweat this chore anymore.

How often should furnace filters be changed? A good rule of thumb says every 90 days. If you have washable furnace filters, cleaning them every 1 to 3 months should allow them to last up to ten years.

Identify Your Filter

Turn off the furnace before you look at your filter.

Remove the current filter located inside the air vent or furnace.

Find the filter size printed on the frame and make a note of it. It’s also a good idea to use a permanent marker to identify what direction the air flows, so you don’t forget the correct way to install your filter.

Find the Right Replacement Filter

Go to your local hardware store or purchase your filter online. You can expect disposable filters to have 1 to 2 inches of thickness.

If you have a furnace that cannot use a thick filter, you need to call an HVAC company for professional help.

Install the Filter

Did you make the mark recommended in the “Identify Your Filter” section? If you did, find it and identify what direction your filter needs to face. Slide the new filter into place and record the date that you replaced it.

Do You Have More Questions About Filters?

There’s more to consider for furnace filters in your home than you may have expected. It’s critical to understand the ratings that work best for your situation.

Now that you know the essentials, what can you do if you still have questions?

Contact us today or give us a call at 303-232-4343. We love talking about all things HVAC.