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Honeywell
Honeywell Cool Moisture Humidifier, 1.1 Gallon, UV Technology, Black, HCM350B
An evaporative humidifier: a UV light treats the water and a wicking filter holds minerals back, so it releases invisible moisture instead of visible mist. A good match for hard-water homes, at the cost of replacement filters.
Updated October 10, 2026
- Listing: 1.1-gallon self-standing tank with up to 24 hours of run time.
- Evaporative design with a wicking filter that captures minerals and a UV system that treats the water (maker description).
- Uses the Honeywell HAC-504 Filter A; one filter is included per the maker page.
- Manual: the water tank is dishwasher safe; the tank cap is not.
- Three fan speeds; the manual calls low speed the quiet setting for nighttime.
- Maker page lists a 3-year limited warranty.
Good for
Bedrooms in hard-water areas where you want to use tap water and avoid white dust.
Skip it if
Very light sleepers bothered by fan noise, or anyone who wants a built-in humidity setting.
Our take
On this page
Our verdict
The HCM350B is the safer bet for anyone filling from a hard-water tap. It is evaporative, the type the EPA says generally disperses less, if any, minerals and microbes than ultrasonic units, and Honeywell says the wick captures minerals to cut white dust. You pay for that with replacement wicks and a fan sound instead of silence. Note what it lacks: the owner's manual describes three fan speeds and no humidity setting, even though the Amazon listing talks about holding a target level. The manual explains that output drops when room humidity is over 60%, so it slows on its own, but keep a hygrometer nearby to stay at or below the EPA's 50% ceiling. The variant trap: HCM350B is the black version and HCM350W the white; both are HCM-350 series and use Filter A.
Filter, UV bulb and cleaning
Honeywell's manual says to soak a new filter in cool water without wringing it, and to remove the filter before any cleaning, because cleaning agents destroy it. Cleaning has two steps in a fixed order: wipe the base, tank cap and tank with undiluted vinegar to remove scale and rinse, then disinfect with 1 teaspoon of bleach in 1 gallon of cool water and rinse until the smell is gone. Do not mix the two. The tank can go in the dishwasher instead of the bleach step; the cap cannot. The UV bulb has an average life of 3,000 hours, and the power light turns red when it needs replacing. A brown, rust-colored filter usually means mineral deposits, per the manual's FAQ.
FAQ
Why can't I see any mist?
The manual says the HCM350 releases invisible moisture, not mist. If the tank level falls over 24 hours, it is working.
Which filter does it take?
Honeywell lists the HAC-504 Filter A as the compatible filter.
Does it have a humidistat?
The manual describes only fan speeds, so use a separate hygrometer to watch the room's humidity.
How we researched this
We read the Amazon.com listing on 2026-10-10, Honeywell's HCM350 product page and the HCM-350 owner's manual, and compared them with EPA guidance. We did not test this humidifier. Honeywell's page gives the tank as 1.1 gallons in its headline and "1 gallon" in its details table.
