How Often Should You Change Your Air Purifier Filter?

Published: July 30, 2025 Updated: May 18, 2026 Nick Kornblith 5 minute read

Depending on your air purifier, you should change your air purifier filter every 6 to 15 months. Over time, pollutants such as dust, allergens, and smoke particles build up and reduce an air purifier’s performance. Knowing how and when to replace the filter is key to ensuring your air purifier delivers optimal air for your needs.

How Often Should You Replace Your Air Purifier Filter?

Your air purifier filter lasts 6 to 15 months, depending on the filter type, purifier model, and usage. Under normal conditions, Alen’s Essential or Advanced HEPA filters for the FLEX or BreatheSmart 45i last 9 - 12 months, 12 - 15 months for the 75i, and 6 - 12 months for the 35i. However, if you live in an area with high pollution levels, wildfire smoke, or allergens, or have pets, you may need to replace the filter more frequently to maintain optimal performance.

Replacing your filter is a simple task that allows your air purifier to continuously capture dust, allergens, and odors, keeping your indoor air clean daily. Most Alen home air purifiers have sensors that allow you to monitor your air via the Alen app, eliminating the guesswork.

HEPA filters – Replace every 6–15 months. These filters capture fine particles such as dust, pollen, pet dander, and mold spores. Homes with pets, smoke, or heavy allergens may need more frequent replacement.
Pre-filters – Clean or vacuum every 1–2 months. Pre-filters capture larger particles such as hair, lint, and dust, helping extend the lifespan of the primary HEPA filter.

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Signs It’s Time to Replace Your Air Filter

If you unexpectedly encounter higher dust accumulation, more sneezing than usual, or if your unit simply doesn't work how it used to, it's probably the filter. Here are common signs that indicate it’s time for a filter change:

Indicator Light or Notification – If your air purifier has a filter replacement alert, trust it and swap the filter. The filter light on an Alen incorporates elapsed run time, particulate level, and fan speed.
Weaker Airflow from the Air Purifier – A clogged filter can restrict airflow, making the air purifier feel less powerful.
More Dust Settling Around the Room – If you’re noticing more dust than usual, the filter may have lost its effectiveness.
Allergy or Asthma Symptoms Are Returning – Worsening symptoms may be a sign the filter isn’t adequately capturing allergens.

A good tip is to jot down a date on the filter when you replace it. If the recommended life span has elapsed but the red light has not yet come one, you might consider replacing it.

Why It’s Important to Replace Your Air Purifier Filter

Replacing your air purifier filter is essential for maintaining clean indoor air and ensuring your system works effectively. A clogged or overloaded filter restricts airflow and reduces your purifier’s ability to capture harmful particles.

According to the Environmental Protection Agency (EPA), particles smaller than 10 microns, such as PM10 and PM2.5, can be inhaled deep into the lungs, contributing to respiratory issues and worsening asthma and allergies.

Replacing your air purifier filter helps:

Maintain optimal air purification performance by allowing proper airflow through the system
Reduce airborne pollutants such as dust, allergens, and smoke particles
Support respiratory health, especially for people with allergies or asthma
Improve sleep quality by maintaining cleaner indoor air overnight

Can I Clean my Air Purifier Filter Instead of Replacing It?

Whether you can clean your air purifier filter instead of replacing it depends on the filter type.

HEPA filters: These are not washable. The fine fibers and electrostatic properties that capture microscopic particles can be damaged by washing or aggressive cleaning, which reduces overall effectiveness.
Pre-filters: These can usually be vacuumed carefully. Regular maintenance helps extend the life of the main filter and keeps your air purifier running efficiently.

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Benefits of Replacing Your Air Purifier Filter

Regularly replacing your air purifier filter is a good way to maintain optimal indoor air quality. Here’s a look at the key benefits:

1. Consistently Clean, Healthy Air

Replacing the filter on your air purifier ensures it continues to effectively remove pollutants from your indoor environment. Over time, filters inevitably become clogged with dust, pollen, pet dander, and mold spores, reducing their ability to capture new contaminants. According to the EPA, indoor air can be more polluted than outdoor air, making a quality working air purifier essential. Regularly replacing the filter ensures that your unit can capture these pollutants, providing you with consistently clean and healthy air. It’s especially important for people with allergies, asthma, or other respiratory sensitivities, as clean air can help alleviate symptoms and improve overall well-being.

2. Better Performance and Energy Efficiency

A clean filter allows your air purifier to operate more efficiently. When a filter is clogged, the unit has to work harder to intake air, which can reduce airflow and purification effectiveness. According to Energy Star, a certification for energy efficiency, maintaining your appliances can lower your energy bills, a win/win for your health and wallet. By replacing the filter regularly, you ensure your air purifier’s optimal performance.

3. Odor Control and a Fresher-Smelling Space

Air purifier filters with activated carbon are designed to trap and neutralize odors. Over time, these filters can become saturated, losing their ability to effectively remove smells from your home. Replacing the filter ensures continued elimination of odors from cooking, pets, smoke, and other sources, leaving your space smelling fresh and clean—a particular benefit for people with odor sensitivities or pets at home.

Final Thought

Maintaining your air purifier with regular filter replacements is essential for clean, healthy indoor air. Recognizing the signs of a clogged filter and replacing it with a fresh one will ensure your air purifier operates efficiently and removes harmful pollutants and odors from your home. At Alen, we want to help you follow a consistent filter replacement schedule with our convenient AutoShip filter subscription service for flexible and convenient filter changes. Ensure your space has air perfectly tailored to your individual needs with Alen.

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