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How to Replace an Air Purifier Filter

Home/Resources/Air Quality/Replace Air Purifier Filter
DH
Written & researched by Derek Holt Home & Appliances Editor
Updated August 2026
Golden-hour view of a person adjusting a floor-standing air purifier in a quiet living room

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Replacing an air purifier filter is a two-minute job anyone can do, no tools required. Replacement filters cost 15 to 80 dollars depending on the model, and there’s nothing hazardous about the swap. But it’s worth doing right, because the common mistakes silently defeat the whole machine: installing the filter still in its plastic wrap, putting it in backward, or washing a true-HEPA filter (which destroys it). Get the orientation right, remove the wrap, reset the indicator, and your purifier goes back to actually cleaning the air.

How to Change Filters for a Honeywell HPA300 Air Purifier — HEPA and Prefilter (eAccess Solutions)

Tools and materials

Low-angle view of a person adjusting a floor-standing air purifier in a quiet living room, in warm late-afternoon light

Step 1: Confirm it’s time

Check the filter indicator light if your unit has one, and look at the filter itself — a true-HEPA filter that’s turned gray or a carbon filter that no longer controls odors is due. Typical intervals are 6 to 12 months for HEPA and 3 to 6 months for carbon, but pets, smoke, and dust shorten them. Reduced airflow from the unit is another sign the filter is clogged.

Step 2: Power off and open the unit

Turn off and unplug the purifier. Open the filter compartment — usually a clip, latch, or twist-off panel on the back or bottom. Note how the old filter sits (which way it faces) before you pull it out, so you can match the orientation of the new one. Slide the old filter out and dispose of it.

Step 3: Clean the pre-filter and housing

If your unit has a washable pre-filter, vacuum or rinse it and let it dry fully before reinstalling — a clean pre-filter extends the life of the pricier HEPA filter behind it. Vacuum dust out of the intake grille and the empty housing while you have access. Don’t wash the HEPA filter itself; water ruins the media.

Over-the-shoulder view of a person adjusting a floor-standing air purifier in a quiet living room, in soft early-morning light

Step 4: Unwrap and install the new filter

Remove all plastic wrap from the new filter — installing one still bagged blocks airflow completely and is the number-one mistake. Find the airflow-direction arrow or the labeled side on the frame and slide the filter in the correct orientation (carbon side toward the intake on combination filters). Seat it fully and close the compartment.

Step 5: Reset the indicator and run it

Plug in and power on. Press and hold the filter-reset button until the indicator light clears (the button and hold time are in your manual) so the change-timer starts fresh. Run the purifier and confirm normal airflow. A proper reset keeps the reminder accurate for the next cycle.

Where to go next

Filter changes are core air-quality upkeep alongside cleaning a humidifier and cleaning a dehumidifier. On a budget, a DIY box-fan air purifier uses replaceable furnace filters instead. It all lives under the air quality hub.

We never buy or physically test the products we rank — our picks come from aggregated owner reviews and expert consensus, explained on how we rank. Follow your purifier’s manual for the correct filter and reset.

Straight Answers

Frequently Asked

How often should you replace an air purifier filter?

It depends on the filter type and your air. True-HEPA filters typically last 6 to 12 months, activated carbon filters 3 to 6 months (they saturate faster), and pre-filters are often washable and reused. Manufacturers print a recommended interval, but real life varies: homes with pets, smokers, wildfire smoke, or heavy dust exhaust filters faster, while a clean, low-traffic room stretches them longer. Many purifiers have a filter-change indicator light as a reminder, but a visibly gray, clogged filter or reduced airflow means replace it regardless of the timer.

Can you wash and reuse a HEPA filter?

No — do not wash a true-HEPA filter unless the manufacturer explicitly labels it as washable. Water damages the dense pleated fiber media that traps fine particles, and a wet HEPA filter can grow mold and lose its filtration ability, so washing ruins it. Pre-filters (the coarse outer layer that catches large dust and hair) are usually washable or vacuumable and should be cleaned to extend the HEPA filter's life. Some purifiers use a 'washable' permanent filter, but genuine HEPA media is replace-only.

Do you remove the plastic wrap from a new air purifier filter?

Yes — always remove any plastic bag or shrink wrap before installing a new filter. New filters ship sealed in plastic to keep them clean, and it's a surprisingly common mistake to install one still wrapped, which completely blocks airflow so the purifier runs but cleans nothing. Unwrap the filter fully, note any 'this side out' or airflow-direction arrow printed on the frame, and install it in the correct orientation. A filter installed backward or still bagged is the top reason a 'working' purifier isn't purifying.

Which way does an air purifier filter face?

Most filters have an airflow-direction arrow or a labeled side printed on the frame — install it so the arrow points the way air moves through the unit (typically the pre-filter or carbon side faces the incoming dirty air and the HEPA side faces the clean-air outlet). Combination filters have the carbon layer facing the intake to catch odors and gases first. Check the frame and the manual; installing a filter backward reduces its effectiveness and can shorten its life. If there's no arrow, the manual's diagram shows the orientation.

How do you reset the filter indicator light?

After installing the new filter, most purifiers need a manual reset so the change-timer starts over — usually you press and hold the filter-reset or a specific button for a few seconds until the indicator light turns off or changes color. The exact button and hold time are in the manual, since it varies by brand. If you don't reset it, the light keeps nagging you even with a fresh filter, or the timer miscounts remaining life. Reset it right after the swap so the reminder stays accurate.