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What filter size do I need?

To start, check the filter in your unit to find the measurements you need. Most filters have the size written on the frame. Generally, the nominal size will be in large print, and the actual size in small print. If no size is listed on your filter, use a tape measure to find the exact length, width, and depth.

Use our size guide chart on any product page to find your nominal filter size.

Where are my filters located?

Your home's heating and cooling system is a significant investment to keep your family comfortable. That's why it's crucial you know where your HVAC system is when moving into a new house, so you can get routine maintenance done quickly. 

Depending on the age and layout of your home and the type of unit you have, your HVAC system could be located in either the basement, attic, garage, or crawlspace. And if you live in a small apartment, your unit is likely in the closet. Once you've located your unit, finding where the air filter is located should be easy with some bit of detective work. 

A common place to find the air filter is inside the blower compartment before the air handler. This location facilitates the removal of dust, pollen, and other airborne particles from the air before it reaches the HVAC system and its essential components. Many different styles of HVAC systems exist, meaning the air filter's location varies. Here are the various types of units and the likely location of the air filter. 

Vertical Up-flow System 

These types of systems are common in North American homes. They are installed upright and circulate air through the side or bottom, pushing it through the top. The location of your air filter in these types of systems can be found at the bottom of the unit. 

Vertical Down-flow System 

Airflow in a down-flow system comes in at the top and flows out at the bottom. These systems are usually installed in closets, and your filter will probably be at the top of the unit. 

Horizontal System 

Horizontal units are usually located in attics and crawl spaces and appear to be lying on their sides. Air flows in from one side of the system through the filter and out the other. Your filter will likely be installed vertically on the side of your return duct for these units. If you still need help finding your filter, we suggest contacting a qualified technician for your next tune-up. 

Colorfil filters are meant for HVAC systems, furnaces, and central air returns, and if the sizing is compatible they can work with air purifiers.

What size filters does Colorfil carry?

Colorfil filters are available in the most commonly used sizes for 1-, 4-, and 5-inch-deep air filters. Here's our complete list of sizes available: Colorfil Size Chart. If you don't see the size you're looking for, don't worry, we're fully capable of building the size you need by submitting a custom order through our 1-inch depth product page or emailing your size to

Custom orders are ONLY available for 1-inch depth filters up to 24 x 30 x 1. 

To submit a custom order, follow these easy steps: 

 1. Click on CUSTOM SIZE under the "Size" section on the product page 

2. *Enter the EXACT dimensions (Width x Height x Depth) in the text fields provided 

3. Continue with the purchase process by selecting your Purchase Options (One-time Purchase or Subscribe & Save)

4. With the Purchase Option selected, press "Add to cart" and continue through checkout

*Custom filters cannot exceed 23.5 (width) x 29.5 (height) x 0.75 (depth) 

If we see any problems or need clarity with the order, you will be contacted within 24 hours from when your order was placed.

How do I change my air filter?

Replacing your air filter is vital to keeping your HVAC system in tip-top shape. When you're ready to replace your filter, here are a few steps for safe and proper replacement. 

The first step is ensuring you have the correct size filter for your unit. The size of your filter will be found on the frame, whether it's a disposable or a reusable, washable filter. For filters that don't indicate size, use a measuring tape to measure the filter's length, width, and thickness. Use these numbers to select and purchase your new replacement filter. 

The second step to replacing your air filter is to turn off your air conditioner or heater via your thermostat. Turning your unit off will help protect your HVAC system from loose dust and dirt from the old filter that could get sucked into your system. Also, it will be easier to replace the old filter without the air pressure of the furnace blower. 

The next step is to remove the old filter. As you do so, please take note of the direction of the arrows on the frame's edge. Insert the new filter with the arrows facing the same direction as those on your old filter. The arrows should point in the direction air is flowing. If you have a ceiling-mounted filter, it should face up. If you are installing a filter next to your unit's blower, it will typically point toward that blower. 

The proper placement is essential to getting the maximum benefit from your heating and cooling system. When replaced incorrectly, it can cause your system to work harder than it should, resulting in higher energy costs. If you follow these steps, you'll be good to go.

What is MERV rating?

If you're looking for the best air filter for your home, it's essential to understand what the MERV rating means. The MERV rating system, which stands for "minimum efficiency reporting value," is a rating system that measures how many particles can pass through the filter and how much airflow it will allow.  

The higher the MERV rating, the more particles it will catch in your home. However, this has a flip side: filters with higher MERV ratings take more force to push air through them because the filtration material is denser. That means less air being able to pass through at any given time—and that can mean raising your energy bill as your system overworks from restricted airflow or even complete system breakdown, costing you high unit replacement costs. 

To find the right filter to use in your home HVAC system, we suggest first checking your HVAC system documentation for maximum MERV limit and then evaluating your living situation and whether or not you have individuals in your home that suffer from mild to severe respiratory disorders. If someone suffers from these disorders, using a higher MERV filter is a good idea.

What is the difference between nominal and actual size?

When shopping for an air filter, it is essential to remember that the air filtration industry standard is to make filters measure slightly smaller than their slot or frame, so they can easily slide into place without getting bent or smashed.  

Nominal Size: Nominal Size is the size you see advertised and printed on the frame of your air filter and is the actual size rounded up to the nearest whole inch. Most filters adhere to this classification system, as it is standard practice within the air filter industry.  

Example of Nominal Size: 16x25x1" 

Actual Size: The actual size of an air filter is typically written in the fine print on the filter frame and is usually 0.25 "-0.5" smaller than the filter's nominal size. The actual size is what you'd find if you used a ruler to measure the exact dimensions of the filter. Actual sizes vary slightly depending on the brand, but in most cases, any standard filter size will work in a typical residential unit.  

Example of Actual Size: 15.5x24.5x0.75" or 15.75x24.75x0.75"

How often should I change my Colorfil air filter?

To maintain high-quality, odorless air in your home, we recommend replacing your Colorfil filters within a week or two of changing to yellow. In the case of accelerated color change, we generally recommend replacing your filters every 30 days. 

As reported by the EPA, changing your filters regularly can improve your home air quality and reduce your energy use and costs. Your unique living environment will determine how regularly you change your filters, including # of occupants, pets, home location, time of year, etc. Unfortunately, it can be challenging to know what's the right cadence for you. Luckily, with Colorifl air filters knowing the right time to replace them is finally very easy.

How should I store my Colorfil filters?

The technology in a Colorfil filter is sensitive to air. For this reason, we encourage our customers to store their filters inside theirplastic, resealable bag in a cool, dry place away from direct sunlight. Keeping your filters this way ensures the filter maintains its entire lifespan. For an extra layer of protection, we encourage holding onto the shipping box to store your filters while in the plastic bag.

My Colorfil filters are changing color too quickly. What does that mean?

Generally, a fast color change is an indicator of relatively high levels of amine-based gas molecules, like ammonia, in your home, which could be from many different sources, like having multiple pets, cooking odors, garbage odors, some paints, floor cleaners, glass cleaners, multi surface chemical cleaners and a lot of other potential sources. These levels can also be amplified if you live in a smaller home or a relatively hot and humid climate. Still, subsequent filters should eventually last longer before they change color once they catch up on existing chemicals and odors and only have to keep up with new ones.

In the case of a fast color change, we recommend you continue to use your yellow filter as a "regular filter" for a few more weeks and replace it on a monthly schedule.

I'm not noticing a difference in my air quality.

Some customers notice an immediate difference in their air, but for others, the change occurs gradually and may even go unnoticed since our noses are so good at adapting to the odors we're exposed to daily. 

Colorfil filters can only eliminate odors and chemicals from the air circulated through your AC system and, in turn, through the filter itself. HVAC systems typically only circulate air when they run their heating and cooling cycles: roughly 20% of the time for most homes. 

To get more out of your air filter, we recommend setting your system fan to "on" instead of "auto" at least for part of the day—especially if you aren't heating or cooling much around this time of the year.

In the case of a fast color change, we recommend you continue to use your yellow filter as a "regular filter" for a few more weeks and replace it on a monthly schedule.

Is the filter coating safe for my family and pets?

The main ingredient in our Colorfil coating is citric acid, a naturally derived, non-toxic chemical found in fruit. Unlike air fresheners, our filters remove chemicals and odors from the air when they come in contact with the surface of the filter without adding any chemicals or artificial fragrances to the air.

What is Colorfil?

Colorfil is a patented filtration technology developed by our founders to effectively clean indoor air from unwanted chemicals, unpleasant odors, and allergens while being safe for all pets and animals. 

The main active ingredient in Colorfil's color-shift coating is citric acid, a naturally derived chemical found in fruit. The coating changes color when it comes into contact with chemicals commonly found in the home. 

Colorfil was created out of personal need. Our founders were dismayed by their family's allergies and environmental sensitivities, but their concerns went beyond their health: they wanted to ensure their pets could breathe easily too.

What is Colorfil's MERV rating?

Colorfil air filters are MERV 8, but they remove more than dust! 

Regular filters only capture large particles, so you still smell that lingering odor after turning on your air system. Colorfil's safe and powerful patented technology captures and binds gas-phase chemicals and odors at the molecular level, which regular filters (even HEPA filters!) cannot.  

This means that in addition to removing 99.97% of airborne particles like pollen and dust mites, you're also eliminating unpleasant and, at times, unhealthy pet, kitchen, and bathroom odors.

What does Colorfil remove?

Colorfil is an air filter technology developed initially for NASA to remove odors in spacecraft and space suits. Over the years, it has evolved into air filtration that reduces many home chemicals and odors. 

Colorfil specifically targets ammonia and amine compounds responsible for many pet, bathroom, and kitchen odors and fumes from household cleaners. It also removes particles in our air, including pet dander and hair, pollen, dust, and other small particulates.

How does Colorfil work?

Colorfil features a built-in color indicator called color-shift that visually shows you it's cleaning your air and when it needs to be replaced. Colorfil changes color from pink to yellow as it attracts, absorbs, and neutralizes chemicals and odors from the air, in addition to capturing hair, dust, and pollen.

How quickly will color change?

If you're new to using a Colorfil Air Filter, you might be wondering how long it will take for the color of your filter to change from pink to orange and then yellow. Everyone's situation is slightly different. Several factors impact this, including the number of pets in your home, how often your HVAC system is running, and the temperature and humidity in your area. So while we can't say with absolute certainty when this will happen in your particular case—it depends on too many factors—we can give a general idea of what to expect. 

Colorfil filters will change color from pink to orange to yellow over four weeks to 4 months. Although we suggest swapping out your filter when it reaches a yellow color, your yellow filter will continue to work effectively against odors and will gradually turn gray as it continues to capture dander, dust, pollen, and hair.

How does Colorfil's subscription program work?

Colorfil is a subscription program that makes getting high-quality air easy and convenient. 

It's simple: To begin, choose the size you need, then tell us how often you want them delivered to your home. We ship directly to your home on the date you need them. When they arrive, remove your old air filter and place your new Colorfil filter. And that's it! 

We currently offer auto-delivery every 1, 2, 4, 6, and 12 months for 1, 2, 4, 6, and 12 packs, respectively. You can adjust your subscription anytime, like changing delivery intervals or delaying your upcoming filter shipment. You're also free to cancel anytime.  

Upon purchasing a Colorfil subscription, you must verify and create an account via the link sent to the email provided upon checkout. Once you've made your account, you can manage your subscription—even if it's on vacation!

How do I cancel my subscription?

To cancel your Colorifl subscription, log in to your account here and click "My Subscriptions." If you need help logging into your account, you can follow the instructions below to access your account, or we can help you by messaging us through our Contact Us page.

Can I pause my Colorfil subscription?

Yes, you may pause your Colorfil subscription by logging into your account HERE and clicking "My Subscriptions" on the left under "My Account". 

On the "My Subscription" page, your current subscription will be visible under "Active Subscriptions." Under the product name, next to the "Next Order" date is "Edit Future order," which you will click, and three options appear. Select "Pause future orders" and click "Save Changes.

After saving, you'll find "Subscription is paused" in yellow, notifying you that your subscription has been paused.

How do I resume my subscription that was previously paused?

You may resume your subscription by logging into your Colorfil account HERE. Once logged in to your account, click "My Subscriptions'' on the left under "My Account." 

On the "My Subscription" page, you'll find your paused subscription just under the "Active Subscriptions" section. To reactivate, click "Resume future orders." Your subscription has been reactivated, and your next order date will be visible.

How do I update my mailing address in my account?

To update your mailing address, please log in to your Colorfil account HERE. After logging into your account, click "My Subscriptions'' on the left just under "My Account". 

On the "My Subscriptions" page, scroll down until you find the "Address and shipping information" drop-down. To review the address on file, click the arrow to activate the drop-down and display the address. To change the shipping address, click "Edit", input the new mailing information, and click "Save Changes".  

Your address has now been updated.

How do I update my billing information?

Please log in to your Colorfil account HERE to update your billing information. Upon logging in, click "My Subscriptions'' on the left, under "My Account.

On the "My Subscriptions" page, scroll down to "Payment Information" and click the drop-down arrow to view your current information. To change your payment information, click on the "Change Payment Information" button on the right, and an email will be sent to the email on file with a secure link to change your payment information. 

In the email, click "Confirm payment information," You will then be taken to a payment page with your current payment information partially displayed. Click "Change" under your payment information and continue by inputting your updated payment information in the appropriate fields. Click "Update" at the bottom of the payment page, and you'll be all set.

Can I cancel my order or subscription anytime?

Absolutely. You may cancel your subscription anytime by logging into your Colorfil account HERE and clicking "My Subscriptions."

How much is shipping?

Shipping is FREE for all orders shipped within the continental United States.

My order arrived damaged. What should I do?

If your product arrives damaged, please contact us and send a picture of your damaged filters here. We will ship you a replacement pack immediately.

I received the wrong size filter. What should I do?

To return your product, please contact us here. Be sure to also include the correct filter size in your message. If you want a different size, be sure to inform us in your message. Following our correspondence, the return process will be as follows: 

The unused product will need to be packed and sent back in the original shipping box. If you don't have the box, you will need to secure a large enough box to fit your filters. 

We will provide a free return shipping label to you. Pack your filters securely, stick your return label on the box, and drop them off at your nearest postal office. 

If you prefer a refund, after we receive your filter, we will inspect it to ensure it hasn't been used or damaged. If everything checks out, we'll issue you a full refund.

I ordered the wrong size filter. What should I do?

No worries, it happens! Please contact us here informing us about the mistake and include the correct size filter.

What Carrier do you use for shipping?

Our filters are shipped with FedEx and UPS. 

Usually,for orders that include 4-packs or more and 4/5-inch filters, we ship through FedEx. For orders smaller than a 4-pack of filters, we ship through UPS.

Do you ship to PO Boxes?

Unfortunately, the standard shipping carriers we use, UPS and FedEx ground, do not deliver to PO box addresses.

How can I track my shipping order?

Tracking information for your order will be sent to the email on file once shipping has been processed. 

If you did not receive an email with tracking information, please confirm that the email we have on file is correct. If it's not, please update the address in your account, after which you'll contact us at for your tracking information.

Does Colorfil offer any promo codes?

Yes, we do. Join our email list through our website pop-up to receive exclusive offers and promotions.

Where are Colorfil filters manufactured at?

Our filters are developed and manufactured in the USA. We are located in Urbana, IL and they are manufactured in-house.