Blueair InvisibleMist H35i Review

This is one of the most sleek humidifiers we have used, and you can pour tap water right in the top as it is running. It is so easy to use this machine, and we are pleased that its year-to-year costs are so low.

Humidification

The secret to the H35i is that it works on evaporative technology. There's a pump depositing water over a filter that a fan pushes air through. The results? A humidifier that has no visible mist.

To be clear, that's not a bad thing. There's some significant benefits here over ultrasonic humidifiers. The major one being distilled or demineralized water is not needed. The normal, dissolved minerals present in all tap waters that would normally get vaporized into a breathing health hazard or left as a white dust haze in your home, are instead left behind on the filter. This is so much easier to fill and run, since you don't need any extra supplies on hand.

The compromise though, is that this machine isn't actively pumping water vapor into the air. It's semi-passively evaporating, which crucially means that there are diminishing returns as a space becomes more humid.

What we found is that starting out, humidity in our tested space shot up rapidly, but over the course of an hour significantly slowed down. Starting at about 40% relative humidity, we saw a cap at a little over 50%.

Ultimately, we feel this isn't too much of an issue, since 50% humidity is still within the ideal range. Other humidification technologies can and will push that number much higher, but that shouldn't be necessary for most households.

Ease of Cleaning

The H35i has a fair number of parts that need to be taken apart to fully clean everything, compared with competitors. The bottom tank is actually quite easy to clean — it's wide open and rounded, so wiping down is a breeze. But you'll need to disassemble the whole unit to do so: the cover, the pump, and the filter all need to be removed to get to the tank.

The filter gets thrown away, so it doesn't need to be cleaned. Blueair recommends replacing every 6 months, which isn't terrible. The pump, though, does not come apart, so it can't really be cleaned in the sink with a sponge.

Noise

The H35i is on the 'louder' side of our lineup, sitting at about 50dB average running noise. In reality, that's about as loud as a quiet conversation or the compressor of an older fridge running.

Practically, you'll only notice the sound of a fan running. No gentle dripping or splashing sounds like other units. And, importantly, it's a constant sound, which effectively makes it double as a pretty solid white noise machine. Blueair specifically markets it as a sleep aid, and we think this would work great in a child's room.

Ease of Use

Thankfully, the InvisibleMist can be filled by refilling straight into the top, which is wide open. Like watering a plant. We do love that, but the tank does still hold almost a gallon (3.5L), so some users will prefer filling in the sink. The tank has a handle, so that's no issue at all.

The few settings this guy does have (3 fan speeds, sleep mode) can be fiddled with via the touch screen on top of the unit. It's a little dim to see and read, but it works fine. If you prefer an App, Blueair has one as well — It's bare bones, but the interface is pleasantly designed.

We measured run time at just over 30 hours on a full tank. That's just about average through our lineup, which makes sense since the tank capacity is about average too.

Operating Cost

This is where the H35i really shows its value, and why we would personally recommend it for anyone looking to run a humidifier constantly. We estimate that, even running all day, every day, all year, it'll cost you around $172. If you're like most average humidifier owners, you'll run the unit for about three consecutive months, which would put the cost at roughly $42.

With units employing Warm Mist tech (steam), you're paying for a lot more electricity usage. Cool Mist (ultrasonic) units, you'll be paying for distilled water or demineralization treatment tablets constantly.

This is the absolutely cheapest unit to run, long term.

Should You Buy the Blueair InvisibleMist H35i?

For anyone with constant humidification needs (but doesn't need relative humidity to over 50%) — this guy can't be beat. A lot of consumers will also be interested in this unit over more powerful competitors as well: No distilled water needed! Save the constant trips to the grocery store, and go for the H35i instead.

What Other Humidifier Should You Consider?