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20x20x4 Air Filter Merv 8 20x20x4 Air Filter Merv 8
20x20x4 AC Filter Merv 11 20x20x4 AC Filter Merv 11
20x20x4 Furnace Filter Merv 13 20x20x4 Furnace Filter Merv 13
20x20x4 Filter Merv 13 Titanium 20x20x4 Filter Merv 13 Titanium
20x20x4 Filter Merv 10 Carbon 20x20x4 Filter Merv 10 Carbon
20x20x4 Filter Merv 8 Carbon 20x20x4 Filter Merv 8 Carbon
Protects All Against
  • Pollen protection
  • Dust protection
  • Mold protection
  • Dust Mites protection
    Dust Mites
  • Bacteria protection
  • Pet Dander protection
    Pet Dander
  • Smoke protection
  • Viruses protection
  • Cooking Smoke protection
  • Odor protection
  • Smog protection

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AC Furnace Air Filter 20x20x4 -Inches

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Product Description

Item Model Number: FKFB20X20X4
Brand: Filter King
Filter size: 20x20x4
Actual Size: 19.5 x 19.5 x 3.75
4-Inch Filter
MERV 8 Filter Rating
Protection From: Pollen, Dust, Mold, Dust Mites, Bacteria, Pet Dander, Smoke, Viruses
Residential / Commercial Use

Manufactured in the US

Why Buy Air Filters From Filter King?


In comparison to fiberglass filters, 20x20x4 pleated air filters are at least 20 times more effective. All Filter King air filters are made in the US.


Filters frames are made out of heat resistant paperboard with horizontal grid supports. Able to withstand temperatures of up to 200° F and resistant to moisture, the paperboard frames do not support microbial growth and outperforms traditional cardboard frames.


Chemical free, electrostatically charged synthetic polyester media is pleated, maximizing the surface area, to capture a high number of airborne particles as small as 0.3 microns with low air flow resistance. To increase durability, the media is supported with a corrosion resistant steel wire.

20x20x4 Air Filter Reviews

What MERV Rating should I choose?

How Often to Change Your 20x20x4 Air Filter?

Filter King AC & furnace filters aren’t the typical fiberglass filters that need to be replaced every 30 days. Our filters can typically be used for 3 to 5 months before requiring to be changed. Naturally, a variety of things influence filter lifespan.

Some of the factors that influence your filter’s life include outdoor air quality, whether pets are in the home, and how well your HVAC system is maintained.

Your air filter becomes clogged over time by trapped particles, preventing airflow. The efficiency of the HVAC filter declines. Your system must work harder to heat and cool your home. The extra strain on the HVAC system causes higher energy bills. Regular home air filter replacements can prevent expensive system repairs or replacements down the road.

You should change your filter more frequently if you notice:

  • Household dust build-up
  • The air isn’t cooling as is used to
  • There’s more dust near the air vents
  • A dirty filter surface
  • Higher energy bills
  • Burning smells near your HVAC system.

20x20x4 Air Filters

AC Furnace Air Filter 20x20x4-Inches

When you purchase a Filter King filter, you can rest assured that you're getting the industry's best 20x20x4 air filter. Our filters deliver clean air to your home by effectively purifying the air as it passes through the filter. They're made of high-quality, durable materials, so you can be confident your filter will hold up well.

100% Made in the USA

All of our 20x20x4 air filters are made in our Alabama warehouse. We take pride in the fact that all of our products are made at our US-based facility, allowing us to keep more jobs and money in the local economy.

Fast Shipping Guaranteed

When you order a Filter King 20x20x4 air filter, we'll ship it to you quickly and free of charge. We also ship your order quickly. How much time it takes for your order to arrive will depend on your location but for non-custom orders it takes between two and five days to arrive. For custom air filters it may take a little longer.

Is It Time to Change Your Air Filter?

Changing your 20x20x4 air filters regularly is essential to maintaining your HVAC system in good condition. Doing so will keep your energy bills low and the system working properly. Homeowners often forget to change their filters for months at a time, leading to maintenance problems and higher energy bills.

Many homeowners wonder how often they should change their 20x20x4 furnace filter or 20x20x4 air filter. A general rule of thumb is that air filters should be changed every 30 days when using inexpensive fiberglass filters. Premium pleated filters may last up to 6 months before needing to be changed depending on use.

There are signs you can look out for to determine if it's time to change your filter.

  • Low airflow: One of the major signs you need to change your ac filter 20x20x4 is low airflow from the vents. Clogged filters prevent air from passing through, so the output through the vents is lower. Changing your filter should restore proper airflow.
  • Dirt or dust accumulation around air vents: clogged air filters may release dirt and contaminants into your HVAC system, which are sometimes expelled through the vents. If you notice dirt around your vents, it may be time to change your filters.
  • Substantial increase in energy bill: A dirty or clogged air filter will cause your HVAC system to work harder to maintain the temperature in your home. If your energy bill increases without explanation, it would be a good idea to check your filters.
  • The filter appears dirty or damaged: You can often determine whether you need to change your filter by visually inspecting it. A damaged filter or a filter covered with dirt, debris or dust, should be changed immediately.
  • Allergies worsen: If you notice you're sneezing or coughing more often than normal, a dirty air filter could be to blame. Changing your air filter will help you determine if it's behind your worsening allergy symptoms.

MERV Rating: Which Should You Use?

MERV stands for Minimum Efficiency Reporting Value. It measures how efficiently an air filter removes airborne pollutants. MERV ratings range between 1 and 20, with 1 providing the least amount of filtration and 20 the highest.

You may think the higher the rating, the better, but that's not necessarily true. The higher the MERV rating, the thicker the filter. A thick filter will force your HVAC system to work harder to circulate air throughout your home, resulting in higher energy bills.

4-6 Rating: Recommended For Industrial Workplaces

Removes Pollen, dust mites, carpet and clothing fibers, cockroach waste, cement dust, hairspray, powders, etc.

20x20x4 air filters with a MERV rating from 4 to 6 work best in medium to heavily trafficked industrial and commercial workplaces. These filters removed large airborne particles that could damage your HVAC system.

They also filter most dust, lint, depending on the MERV rating chosen. Air filters with a MERV rating of 6 are much more effective than regular inexpensive fiberglass filters. At this level, the filter will remove large particles such as dirt, debris, and lints.

8-13 Rating: Recommended For Home Use

Removes Lead dust, Legionella bacteria, milled flour, welding fumes, dust from humidifiers and nebulizers, coal exhaust, smog.

Air filters with a MERV rating from 8 to 13 more effectively filter your air than less expensive lower-rated filters. The higher the rating, the cleaner the air in your home. For better protection against airborne contaminants and high air quality, this category is recommended.

If you or a family member suffers from allergies, you should consider investing in a 20x20x4 air filter with a MERV rating between 11 and 13 to ease your symptoms. At lower ratings, particles such as pet dander, fine dust, and pollen may slip through your filter. A filter rated between 11 to 13 will adequately remove most allergens from your home's air.

In addition to removing common pollutants such as dust, pollen, lint, and mold, a 20x20x4 air filter MERV 11 rating filter’s enhanced filtration efficiency allows it to remove smoke, smog, coughing, and sneezing particles, and pet dander.

20x20x4 furnace filters and air filters rated MERV 13 are the best overall filter you can buy for use in a residential air conditioner or furnace. At this rating, air filters effectively capture and remove a high range of particles, including bacteria, smoke, and some viruses. If you or a loved one are illness prone and need a clean, sterile environment, a MERV 13 rated air filter is worth considering.

14-20 Rating: Recommended For Hospital & Laboratories

Removes: Bacteria and viruses, sneeze and coughing droplets auto emissions and fumes, tobacco smoke, insecticide dust, face powder, microns, radon, carbon dust, salt, combustion emissions, dust lint, etc.

Air filters at this level are primarily used in facilities where airborne contaminants must be eliminated, such as hospitals and laboratories. They are not recommended for residential use because they restrict airflow, and most residential HVAC systems are not equipped to handle them.

FAQs: Common Questions

In case you have any lingering doubts about 20x20x4 air filters, we have put together a list of the most frequently asked questions.

When Should I Change an Air Filter?

The type of filter you own will determine how often you should change it. You should change cheap fiberglass filters every 30 days. Change pleated air filters and furnace filters every 90 days.

If someone in your home suffers from asthma or severe allergies, you should change your filter every six weeks to ensure your home has the best quality. If you have pets, you may want to consider changing your filter every two months.

If you notice your air filter is clogged or dirty, you should change it immediately. If you notice dirt building up around your vents, check to see if your filter needs to be changed.

What MERV Rating Filter Should I Pick?

If you're purchasing an air filter 20x20x4 for home use, you should select a filter with a MERV rating from 8 to 13. At this rating, the air filter will efficiently remove allergy-causing particles and allow you to breathe comfortably. For homes with pets and allergy sufferers, MERV 13 filter works better.

If you use your filter in an industrial workplace, choose an air filter with a MERV rating between 4 and 6. For hospital use, choose an air filter with a MERV rating of 14 or higher.

Do You Have Warranty on Your Filters?

Yes. If for any reason you're not satisfied with your purchase, you can return your to us filter up to 30 days after purchase. All items must be returned in their original condition and original packaging.

We do not accept returns of customized air filters. Customers are responsible for all return shipping costs. You can return items to us using your own shipping label.

Do You Offer Discounts on Bulk Purchase?

Yes. We offer discounts on bulk purchases. Buying more filters at once also means that you’ll get free shipping for your order. Customers only need to order two or more filters at once to take advantage of Furnace King’s free shipping offer. Please contact us for more information.

How Long Does the Shipment Take?

Shipping with Furnace King is fast, convenient, and with an order of two or more filters, free. Orders from within the contiguous U.S. generally take up to two days to process, while international and custom orders can take up to five days.

Most of our filters ship within two business days. Once an order has gone through, shipping takes three to five business days for orders within the United States.

Filter King: Air Filter Delivery Service

If you want to ensure you always receive replacement 20x20x4 air filters when it's time to replace your old ones, consider signing up for our air filter delivery service. All you need to do is follow 3 easy steps to be sure you have the cleanest air possible circulating through your home.

To subscribe to the air filter delivery service, tell us what size air filters you need, how many you need, and how often you'd like them delivered. We will auto-ship the air filters you need based on the schedule you select. There are no contracts or obligations, and you can cancel this service at any time.