The Perfect Guide on How Often to Change an Air Purifier Filter

by Véronique Raymond
hands changing air dust carbon and hepa purifier filters

There’s no denying that air filters are found in various places in your home. They are generally installed in air ventilation and heating systems such as furnaces and air conditioners. Their sole purpose is to elevate the indoor air quality of your living space.

Nevertheless, given that homes can be tedious to maintain, filters are often the last thing on people’s minds are usually forgotten. This guide will walk you through how often to change an air purifier filter and the repercussions of skipping this process.

Why You Should Replace Your Air Purifier Filters

When an air purifier is running in your home, you and your family get to enjoy refreshing, clean air that’s free of allergens and irritants. That’s because these pollutants have been trapped in the filter.

As the air makes its way through the purifier, pet dander, dust, particles, and allergens get entangled and build up after a while and saturate the filters. The same applies to adsorptive options such as carbon filters that absorb chemical fumes and odour molecules in the air.

A filter that’s littered with contaminants slowly loses its efficacy. Besides running low on space for newly-trapped particles, air doesn’t pass efficiently through saturated filters. Resultantly, frequently replacing an old filter with a new one ensures your air purifier functions optimally.

Do All Filters Require Replacement?

Some manufacturers have recognized the need for models that require lower maintenance costs, ushering in the development of air purifiers with permanent or washable filters. These models diminish or eliminate the need to frequently buy replacement filters. Nevertheless, these filters still require consistent cleaning by vacuuming or washing to maintain efficiency.

In a nutshell, regardless of whether you have permanent, disposable, or washable filters in your air purifier, they all come with a lifespan. To prolong the filter lifespan, they must be cleaned or replaced frequently as part of the maintenance and care requirements.

How Often to Change an Air Purifier Filter

If you live alone with no children or pets and don’t have allergies, switching the filter every 6 months is usually enough. Nevertheless, various factors affect how frequently a filter replacement is required.

1. Type of Filter

The lifespan of your filter varies based on the type and quality. The filter quality is determined by the MERV level, an acronym for Minimum Efficiency Reporting Value coupled with the material used. A greater MERV value means that the least amount of particles can pass through the filter. Therefore, for optimum efficiency, choose a screen with a MERV value of at least 8.

Washable Filters

These are constructed with a thread-like mesh. While they are reusable, they provide the lowest level of filtration (MERV 1 to 3). They’ll stop fur, pollen, dust, and hair but are ineffective against other pollutants such as spores, dust mites, and smoke. Therefore, washable filters require replacement every month or once per 3 months.

Fibreglass Filters

These types of filters are affordable and usually feature MERV levels ranging from 2 to 4. Contrary to washable screens, fibreglass filters can trap dust mites. Nevertheless, this screen type requires replacement every month or once after 3 months.

AirThreds 16x25x1 Air Filter for AC HVAC Furnace, Machine Washable & Dryer Friendly MREV 8 Plus Reusable Air Filters

Source: Amazon

Pleated Filters

These are the more expensive options compared to the washable and fibreglass counterparts. Pleated filters have the uncanny ability to trap more dirt as they have a MERV level of 6 to 10. While some top-grade pleated filters require replacement after 6 months, a standard one should be swapped every 3 months.

Electronic Filters

These screens are electromagnetically charged for enhanced efficiency. Electronic filters have a MERV ranging from 8 to 16. Compared to other types of filters, they can also trap smoke and viruses.

Electronic filters are pricier and are only compatible with particular HVAC systems. These filters only require replacement once a year, making them a popular choice for those limited with time for filter care and maintenance.

HEPA Filters

These are the crème de la crème of filters with a MERV level ranging from 17 to 20 and filtering up to 99.99% of all air contaminants. Despite their high price point, they require replacement every 6 months. Nevertheless, some pleated HEPA filters can last up to 2 years.

2. Filter Thickness

Screens vary in thickness ranging from 1 inch to 5 inches. The thicker the material, the more durable and sturdier it is and the more dirt it can hold.

  • 1 inch: A maximum of 3 months 
  • 2 inches: Up to 4 month
  • 4 inches: 6 to 8 month
  • 5 inches: Up to 1 year

3. Special Circumstances

Under the following conditions, you might want to replace your air purifier filter more frequently.

Asthma and Allergy

If anyone in your household suffers from these underlying conditions, it’s best to change the filter after every 4 to 5 weeks.


Cats and dogs not only shed hair but also emit strong odours between seasons. If you own a pet, a filter replacement every 2 months should be sufficient. However, if you have several pets living in your home, changing the air filter once a month is advisable.


Toddlers and babies are sensitive to the quality of air. Therefore, you should switch out your air filter at least every 2 to 3 months to make sure they breathe contaminant-free air.

Heavy Use

If you’re constantly using a heating or air conditioning system, interchanging the filters every 4 weeks is required. Contrarily, if it’s your secondary home, having an inspection done by a professional, every 5 to 6 months should suffice.

Home Size

The bigger your home is, the more air flows through it, which requires more regular maintenance.

Outdoor Air Quality

It’s essential to factor in the quality of the air outside your home. If you reside in a highly polluted area adjacent to a highway or busy road, we recommend having your filter inspected more frequently (every month).

4. Quality of Water

The water quality impacts the longevity of washable filters in your home. Tap water filled with mineral deposits can compromise the lifespan of your filter since they cause clogging.

Signs Your Filter Requires Replacement

If your air purifier lacks a filter change indicator, you can also determine if a replacement is due by keeping your eyes peeled for the following telltale signs.

  • The filter exhibits a gray tint with visible dirt and dust buildu
  • Your home is dustier than usual 
  • There’s a noticeable increase in pet dander in the ai
  • You and the members of your household are experiencing more severe allergy symptoms or asthm
  • You’re beginning to notice poor smoke control and odour

Do You Need to Dry Your Washable Air Purifier Filter After Cleaning?

Yes! It’s essential to thoroughly dry washable purifier filters before re-installing them back in your unit. Failure to do so may result in the formation and growth of mould, making your unit emit a pungent smell.


Replacing your air purifier filter frequently is the secret to maintaining clean air in your home. Although most filters require replacement every 3 to 6 months, the quality, presence of pets and children, allergens, and pollutants such as smoke, call for more frequent maintenance and care.


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