How often should you replace a humidifier filter?
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The short answer
There’s no single number. Honeywell says to replace its wicking filter about every 30 to 60 days, depending on use and water quality. Levoit’s manual doesn’t give a set interval for the sponge filter in its ultrasonic models, so replace it when it looks discolored or worn, smells off, or your model’s filter reminder comes on. EPA says to follow the manufacturer’s instructions on replacing the materials that come with your humidifier. Check your manual first, and use the signs below to adjust.
Two kinds of “filter”
In an evaporative humidifier, the wick is the part that soaks up water so a fan can blow moisture into the room. That’s what Honeywell’s 30 to 60 days refers to. Levoit’s ultrasonic models take a different filter, one that sits in the tank and catches impurities from the water. Look up which one you have before you plan a schedule. If you’re not sure which wick fits, see HAC-504AW vs HFT600, or use Find my filter.
Signs the filter is done
Honeywell’s list for a wicking filter:
- It feels stiff, hard, crusty or brittle.
- Heavy mineral deposits cover it.
- It has holes, tears or collapsed sections.
- It has a persistent unpleasant odor.
- The top stays dry while the bottom stays wet.
- The humidifier uses water more slowly, or the room doesn’t get more humid even with the fan turned up.
Honeywell adds that yellow or brown color alone doesn’t always mean the filter has mold, because minerals can change the color. Replace it when the color comes with stiffness, crusting, odor, damage or lower output. The manual for the Honeywell HEV355 says a light brown or rust-colored filter is probably a mineral deposit, and suggests soaking it in cool water to help break up deposits.
Hard water shortens a filter’s life
As water evaporates from a wick, the dissolved minerals stay behind and gradually harden in the fibers. Honeywell says soft water and occasional use can let a wick last toward the long end of its range, while hard water, daily use and high settings can call for a change sooner. A cool-water soak may loosen some buildup for a while, but Honeywell says it doesn’t make a worn filter new again. EPA’s advice for cutting minerals is low-mineral water such as distilled water. That’s also the fix for white dust from an ultrasonic humidifier.
Make a wick last
- Flip it 180 degrees, top to bottom, at each tank refill. Honeywell says this keeps the wick evenly wet, since the top dries faster.
- Use fresh water. Honeywell says not to keep topping off old tank water.
- Never wash the wick with soap, vinegar or bleach. Take it out before you descale or disinfect the humidifier. Honeywell says these chemicals can damage the filter.
- Soak a new wick in cool water and don’t wring or squeeze it. Honeywell’s manual and guide both say so.
- Match the filter letter and part number to your model. A similar-looking wick may not fit.
At the end of the season
EPA says to clean the humidifier when the season ends, make sure every part is dry before it goes into storage, and throw out used filters rather than saving them. Honeywell’s guide says to put in a new wick at the start of the next season.
Quick checklist
- Manual checked for your model’s schedule
- Wick or filter inspected for stiffness, crust, odor, holes or a dry top
- Wick flipped at each refill
- Low-mineral water if your water is hard
- Right part on hand (Find my filter)
More: how to clean a humidifier · what humidity to aim for this winter · all tips