Honeywell
Honeywell HUL535 Filter-Free Cool Mist
No longer sold by Honeywell in the US Honeywell's own store lists the HUL535 as discontinued and no longer available for purchase (October 2026). Shown for comparison.
Honeywell's filter-free line exists because plenty of people would rather buy no consumables than buy the right ones. There is no wick and nothing to replace, which keeps ownership about as cheap as it gets here - and it is an ultrasonic with no demineralisation media, so on hard water the minerals that a wick would have caught end up on the furniture instead. A gallon tank and 24 hours works out to about a gallon a day, near enough to what its 300 sq ft claim needs, making this one of the more honest small ultrasonics on that particular number.
The room-size claim, reconciled
246 sq ft supported · box says 300 sq ft
The box says 300 sq ft; the winter load calculation puts the output at 246 sq ft — an overstatement of about 22%, which is modest for this category.
Holding 300 sq ft takes about 1.22 gal/day, which drains this 1-gallon tank in roughly 20 hr — against the 24 hours Honeywell advertises, which is measured at the lowest setting.
What a year costs
no filter or wick. Electricity assumes the rated 38 W for 12 hours a day across a 150-day heating season at 16¢ per kilowatt-hour.
Specifications
Maintenance profile
- Top fill
- No — tank comes off and goes to the sink
- Replaceable media
- None — nothing to buy
- White dust risk
- Yes — atomises minerals with no demineralisation
Facts, not a score. Which of these matter depends entirely on whether the unit ends up somewhere you will actually clean it.
Features
- No filters or wicks ever
- 1-gallon tank, 24-hour run
- Variable mist dial
- Auto shut-off when empty
Pros
- No consumables at all - the only ongoing cost is electricity
- Runs a full 24 hours on a tank at a mist level that roughly matches its claimed room size, which is rare here
- Simple enough that there is very little to go wrong
Cons
- White dust on hard water, with no demineralisation option built in
- No humidistat, so it cannot stop itself over-humidifying a closed room
- Bottom-fill tank, so every refill is a trip to the sink carrying it upside down
- The ultrasonic disc scales in hard water and needs descaling to keep output up, which the manual covers but the box does not
The pros and cons above are drawn from the maker’s documentation and published specifications. There is not yet a body of owner reports for this model that we have read.
What owners say
No owner discussion collected for the Honeywell HUL535 Filter-Free Cool Mist yet. The pros and cons above come from the maker's documentation and published reviews, and this section will fill in when there is enough first-hand material to summarise honestly. We would rather leave it empty than invent it — how we compare explains why.
Honeywell HUL535 Filter-Free Cool Mist, head to head
Looked at alongside it
More from Honeywell →
Take the HCM-350's mechanism and move the fill to the top: water goes in through a funnel on the lid, so nothing has to be carried to the sink, and that is most of what "Easy to Care" means. The trade is capacity: a 1-gallon tank against the 350's 1.1, no UV, and no humidistat here either. Neither Honeywell's manual nor its store page says any part is dishwasher safe, unlike the HCM-350, whose tank and tray are. At the 36 hours Honeywell claims it is moving two thirds of a gallon a day, which is a bedroom's worth; the 360 sq ft it is sold for would take closer to 1.5 gallons a day and drain the tank in about 16 hours.
165 sq ft supported · box says 360 sq ft
The long-running default in this category, and the arithmetic explains why. Honeywell's manual gives 2 gallons a day of output against the 500 sq ft it is sold for - a room that needs almost exactly that - making this one of the few portables in the catalog whose coverage number the physics supports outright. It was sold from 2011 largely unchanged until Honeywell discontinued it; the tank and tray go in the dishwasher, and it evaporates rather than atomises, so there is no white dust. The costs are a wick habit, a fan you can hear, and no humidistat at all: three speeds, and you are the humidistat.
493 sq ft supported · box says 500 sq ft
Crane's fix for the original Drop's two real problems - the bottom-fill tank and the neck you could not get a hand into - plus a sound machine and a colour-changing nightlight aimed squarely at nurseries. The top opening is wide enough to reach inside and scrub, which is the single most useful change and the reason to pay $5 more. Three sleep sounds, an aroma tray for vapour pads, and the same one-gallon, twenty-four-hour, no-filter arrangement underneath.
246 sq ft supported · box says 500 sq ft