How Often to Replace a HEPA Filter: Maker Intervals Compared
How often to replace a HEPA filter, with the intervals Levoit, Coway, Winix, Honeywell, Blueair, Medify, Austin Air and IQAir state, and the signs a filter is due.
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Replace a purifier's HEPA filter as often as its maker says, which for most home purifiers is every 6 to 12 months of regular use, and sooner if the purifier runs around the clock, you have pets or smokers, or there has been wildfire smoke. Carbon filters and carbon layers usually need replacing sooner than the HEPA media behind them. A few premium purifiers use filters rated for four or five years.
Makers rate filters by run time, not the calendar. A filter rated for 12 months at 8 hours a day lasts about 4 months at 24 hours a day. Most purifiers now count fan hours and light an indicator when the filter is due; trust that over a date, and trust your nose and your eyes over both.
Makers' stated intervals
| Purifier | HEPA filter | Carbon or pre-filter | Source |
|---|---|---|---|
| Levoit Core 300-P | Every 6 to 8 months | Combined filter | Levoit |
| Coway AP-1512HH, Airmega 200M | 1 year | Deodorization filter 6 months | Coway filter set |
| Coway Airmega 400 | About 1 year (Max2 set) | Combined in Max2 | Coway |
| Winix 5510 | About 12 months | AOC carbon about 12 months; wash pre-filter every 14 days | Winix manual |
| Winix AM90 | 12 months | Carbon 3 months | Winix |
| Honeywell HPA300, HPA200 | 12 months | Carbon pre-filter 3 months | Honeywell store |
| Blueair Blue Pure 211i Max | Up to 9 months (EcoLast: 18) | Washable fabric pre-filter | Blueair |
| Medify MA-40 | 3,000 hours, about 4 months 24/7 | Combined | Medify |
| GermGuardian AC4825 | 6 to 8 months | Carbon pre-filters 2 to 3 months | GermGuardian |
| Alen 75i | About 12 to 15 months 24/7 | Combined | Alen |
| Molekule Air Pro | About 6 months | Combined PECO-HEPA | Molekule |
| IQAir HealthPro Plus | 48 months (HyperHEPA) | V5-Cell 24, PreMax 18 months | IQAir US |
| Austin Air HealthMate | 5 years | Combined | Austin Air |
Why run time matters more than months
A filter fills up with the particles it catches. Run the purifier twice as many hours, or in air with twice the particles, and it fills twice as fast. Medify states its interval in hours (3,000) for exactly this reason. Convert any interval to your use:
| Hours a day | Months |
|---|---|
| 8 | 12 |
| 12 | 8 |
| 24 | 4 |
Most makers do not say what daily run time their month figure assumes, so treat the filter indicator, which counts real hours, as the better guide.
Signs a filter is due
- The indicator says so. Reset it every time you fit a new filter, or it will be wrong next time.
- Less airflow from the outlet on the same speed.
- The purifier is louder as the fan works against a clogged filter.
- Smells come back. Carbon stops adsorbing when it is full, often well before the HEPA media is loaded.
- The filter is visibly gray or dark on the intake side. White media turning gray is normal; dark gray or black, especially after smoke, means change it.
- A monitor shows higher PM2.5 than usual with the purifier running.
When to replace sooner
- Wildfire smoke. Smoke loads filters quickly; EPA research on DIY air cleaners found them almost completely ineffective with dirty filters. Keep a spare before fire season.
- Pets and smokers. More particles and odors mean faster loading, especially of carbon.
- Renovation dust. Sanding and drywall dust clog filters fast.
- Damp or musty filters. A filter that has been wet or smells musty can grow mold; replace it.
Can you clean a HEPA filter instead?
Generally no. HEPA media is a mat of fine fibers; washing or vacuuming it can damage the fibers or leave gaps, and water can encourage mold. Most makers say the HEPA filter is not washable. Pre-filters are different: many are designed to be vacuumed or rinsed, which extends the life of the HEPA filter behind them. Our guide to cleaning an air purifier covers what you can and cannot wash. A few filters, such as some electrostatic and permanent designs, are made to be washed; follow the manual.
Genuine or third-party?
Third-party filters cost less but have not been checked against the purifier maker's specification, and a poor fit lets air bypass the filter, which lowers the real CADR. Some makers tie warranties to genuine filters. If you try a third-party filter, check that it seals snugly in the housing. Our True HEPA explainer covers what the labels on them mean.
Budget for filters when you buy
A cheap purifier with an expensive, short-lived filter is not cheap. Before you buy, check the filter price on the maker's own store and work out a year; our best air purifiers list does this for each pick.
Frequently asked questions
How often should you change a HEPA filter in an air purifier?
Follow the maker's interval, usually every 6 to 12 months of regular use, and sooner with 24/7 running, pets, smoke or renovation dust. Some premium filters last four or five years.
How do I know when my air purifier filter needs replacing?
The filter indicator, weaker airflow, a louder fan, returning smells, or a filter that is dark gray on the intake side all suggest it is due.
Can you wash a HEPA filter?
Generally no; washing or vacuuming can damage the fine fiber mat and water can encourage mold. Pre-filters are often washable. Follow the manual.
What happens if you do not change an air purifier filter?
Airflow drops as the filter clogs, so the purifier cleans less air, gets louder, and its carbon stops removing odors. A damp, neglected filter can also smell musty.
Do carbon filters need replacing more often than HEPA filters?
Often, yes. Carbon stops working when its surface is full of adsorbed gases, which can happen well before the HEPA media is loaded. Winix rates the AM90's carbon for 3 months against 12 for its HEPA.
Are generic air purifier filters as good as genuine ones?
Sometimes, but they are not checked against the maker's specification, and a loose fit lets air bypass the filter. Some warranties require genuine filters.
Sources
- Levoit Core 300 Series Original Filter, Levoit
- Coway Airmega Mighty AP-1512HH & 200M Filter Set, Coway
- 5510 & 5520 User Manual, Winix America
- Honeywell True HEPA Air Purifier, HPA300, Honeywell Store
- MA-40 Air Purifier Replacement Filters, Medify Air
- Research on DIY Air Cleaners to Reduce Wildfire Smoke Indoors, US Environmental Protection Agency
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