LEVOIT OasisMist 4.5L Review: a smart warm/cool humidifier that’s good, but fussy to live with

I’ve been using the LEVOIT OasisMist 4.5L in my bedroom and home office for a bit, mainly because dry air wrecks my sinuses in winter. I wanted something quiet, with auto humidity control, and ideally warm and cool mist in one unit. On paper, this one ticks pretty much every box: app control, warm/cool mist, auto mode, big tank, essential oil pad, the whole package. It sits in that mid-to-high price bracket, so I expected something fairly polished.

In practice, it does the core job: it puts moisture in the air and keeps the room more comfortable. My nose and throat feel less dry overnight, and I’m not waking up with that sandpaper feeling like I do without a humidifier. The app is genuinely useful for setting a target humidity and just forgetting about it most of the time. Noise-wise, it’s quiet enough that I can sleep with it a few feet from the bed without it bothering me.

But once you get past the basic "it works" part, you start noticing the small design choices that make day-to-day use either nice or slightly annoying. Things like how easy it is to clean, how the lid behaves, how the tank sits on the base, and how the controls are laid out. That’s where this model is a bit of a mixed bag. Some stuff is well thought out, some stuff feels like the engineers never actually used it in a dark bedroom at midnight.

Overall, my impression is that it’s a pretty solid humidifier with smart features, but with a few quirks that might bug you depending on how picky you are. If you just want something you fill, set to auto, and don’t mind occasional fiddly cleaning, it’s fine. If you obsess about cleaning, hate awkward lids, or expect premium polish for the price, you might end up slightly annoyed, like I did at times.

Price-wise, this sits on the higher side for a home humidifier of this size, especially if you catch it at around the $110–$120 range. For that money, you’re getting warm and cool mist, smart app control, auto humidity, and a 4.5L top-fill tank. Those are strong features, and to be fair, the app experience is one of the better ones I’ve seen on a humidifier. If smart control and dual-temp mist matter a lot to you, then the price is easier to swallow.

But if you strip away the smart stuff and just look at it as "a thing that adds moisture to the air", the value becomes more debatable. You can get simpler humidifiers that humidify just as well for less. One user compared it to a cheaper brand (around $80) that had most of the same features and was easier to clean, and ended up keeping the cheaper one. I get that. At this price, I’d expect them to nail the basics like cleaning access, lid ergonomics, and maybe include a better mineral filter option.

Where it redeems itself a bit is convenience: the app scheduling, auto mode, quiet operation, and top-fill do make daily use nicer than a barebones unit. If you’re into smart home setups, being able to tweak humidity from your phone or tie it into routines has real value. Also, the combined warm/cool mist means you don’t have to buy two separate devices or a more expensive one later just for warm mist.

For me, I’d call the value decent but not outstanding. You’re paying a bit of a premium for smart features and dual mist, but you’re not getting a super polished, zero-annoyance product in return. If you find it on sale or you really want the app control, it’s easier to recommend. If you just need something to keep your nose from drying out and don’t care about Wi‑Fi, there are cheaper, more straightforward options that will get the job done with less fuss.

Design-wise, it’s a clean white rectangular unit that doesn’t look ugly in a bedroom. It’s compact enough (about 10.8"D x 6"W x 12"H) that it fits on a dresser or nightstand without taking over. The dual 360° nozzles on top are actually one of the better parts of the design. Being able to point mist in two directions is handy if you don’t want a jet of mist blasting straight at your head in bed. You can aim one toward the middle of the room and one away from walls, which helps avoid condensation on nearby surfaces.

Now, the lid and tank orientation are where the design gets annoying. There’s a finger slot under the front of the lid so you can lift it, but a few times the lid kind of slipped and ended up falling into the water. It’s not the end of the world, but when you’re refilling this thing at night and the lid drops into the tank, it’s just irritating. Also, the tank isn’t perfectly symmetrical, so you need to learn which way it faces to sit correctly on the base. After a while you get used to it, but the first week I was constantly rotating it like a puzzle piece.

The control panel is on the front with touch buttons and a display. The text labels are clear, which I like, but there’s no beep feedback when you press a button. Some people prefer silence, but I like a small beep just to know it registered my tap. Also, if you want the screen totally dark at night, you can’t do that from the unit itself – you have to use the app to turn the display off. Again, not a huge deal, but for a bedroom device, a simple "screen off" button on the body would’ve made more sense.

Access to some parts for cleaning is also not ideal. The top nozzle section doesn’t just pop off easily; you basically have to be careful and sometimes use tools to get into the tight areas if you want a proper scrub. For a product that sits in warm, damp conditions all the time, making every part simple to disassemble and clean should be a top priority. Here it feels like design aesthetics slightly won over practicality.

From a comfort standpoint, it helps with dry air symptoms. After a few nights running it in my bedroom, my sinuses felt less irritated, and I wasn’t waking up with a dry throat. If you deal with congestion or that tight chest feeling in winter, having some extra humidity in the room genuinely makes sleep more pleasant. The option to use warm mist is nice when the room is chilly – the air feels less cold and harsh, even if it’s not actually heating the room.

The unit is quiet enough for light sleepers, especially in auto or low mode. There’s no loud fan ramping up and down, just a soft hum. The lack of button beeps is a double-edged sword: on the one hand, you can adjust it at night without loud beeping; on the other hand, you sometimes don’t know if your tap registered without looking at the screen. I ended up mostly controlling it via the app from bed, which kind of solves that.

Top-fill is a big plus for comfort of use. Being able to just lift the lid and pour water in from a jug is way nicer than flipping a tank over in a sink and trying not to spill. The downside, like I said earlier, is that the lid design isn’t perfect and can fall into the tank if you’re not careful. When you’re tired, that kind of thing gets old fast. Also, figuring out the tank orientation the first few times is mildly annoying; it’s not super intuitive.

One more comfort-related thing: cleaning. If you’re the type who likes low-maintenance gear, this might feel like a chore. You need to stay on top of rinsing and weekly deeper cleaning to avoid slime and mold in the hard-to-reach spots. The included brush helps, but there are still tight areas that take patience. If you ignore cleaning, any ultrasonic humidifier will get gross, and this one is no exception. So comfort-wise, breathing is better, but your cleaning routine gets a bit heavier.

In terms of build, the plastic feels decent for the price range – not super cheap, but not high-end either. The unit is fairly light (around 5.3 pounds empty), so moving it from room to room is easy. I didn’t notice any leaks or weird creaking, and the base feels stable enough on a flat surface. The tank handle and general structure seem solid enough to handle regular refills without feeling like they’ll snap off.

Where durability gets tested is really in how well it deals with minerals and biofilm over time. This is where I’m a bit skeptical. The design has quite a few small cavities and narrow spaces where water sits, and those are exactly the places that start building up scale and slime if you’re not religious about cleaning. One reviewer even mentioned cleaning it daily and deep-cleaning weekly, plus using additives, and still dealing with mold in hard-to-reach areas. That doesn’t scream low-maintenance to me.

If you use tap water with minerals, you’re going to see white dust and calcification on and around the unit over time. LEVOIT includes a little sponge filter, but it’s not a real mineral filter like some other systems. So, realistically, if you want to keep this thing running nicely for a long time, you should plan on using distilled or RO water. That adds to the long-term cost and effort, but it’s pretty standard for ultrasonic humidifiers unless they have a serious filtration system built in.

Long-term, I think the electronics and motor will probably hold up fine as long as you don’t let gunk build up inside. The app connectivity and Wi-Fi aspect didn’t give me any issues. But if you’re lazy with maintenance, durability is going to suffer quickly, and you’ll probably start hating the cleaning process. So it’s not fragile in the sense of breaking immediately, but it’s not a set-and-forget unit either. It will last, but only if you’re willing to put in the cleaning work.

On raw performance, it humidifies well enough for a bedroom or small living room, especially if your air isn’t desert-dry. The 4.5L tank lasts most of the day or a full night on moderate settings. On the highest mist level, it pushes out a strong stream of mist that you can clearly see, and it ramps up humidity fairly quickly in a 200–300 ft² space. In my bedroom, going from around 25–30% to somewhere in the low 40s over a couple of hours was pretty standard.

However, if you live in a very dry climate, you might notice the limits. One user mentioned a 200 ft² desert room where it struggled to get above 40%, and that lines up with what I’d expect from an ultrasonic unit of this size. It’s fine for comfort, but if you’re expecting rock-solid 50%+ humidity in harsh conditions, this might feel a bit underpowered unless you run it hard and close doors. The auto mode tries to maintain the set level, but depending on your room size and dryness, it may just hover a bit below your target.

Noise levels are good. On low and auto, it’s basically a soft hum with some light water sounds, around that "whisper-quiet" zone they advertise. I had no problem sleeping with it on. Warm mist mode adds a bit of fan/boiler noise but nothing crazy. It’s still much quieter than older evaporative units I’ve used. The app control and sensor are another story: the built-in humidity sensor is reasonably accurate, but you really don’t want to place it right next to the unit and trust that number as "room humidity". A separate hygrometer across the room gives a more realistic reading.

One thing that bugged me is the sleep mode logic. Sleep mode basically runs at a low mist level but doesn’t have smart cutoffs to stop at a certain humidity, so your room can end up more humid than needed if you leave it all night. I prefer using auto mode with a set percentage and screen off, which is more controlled. Overall, performance is decent and very usable, but it’s not some miracle machine. It does what a mid-range ultrasonic humidifier should do, nothing more.

Out of the box, you get the humidifier body, the 4.5L tank already attached, an aroma pad, a little cleaning brush, and a water filter sponge. No assembly needed, which I appreciated – you basically rinse the tank, drop in the sponge, fill it, and you’re ready to go. It’s an ultrasonic unit with both warm and cool mist, and it’s meant for rooms up to around 430 ft², which is roughly a medium bedroom or small living room.

The main selling points on paper are: top-fill tank, smart VeSync app control, auto humidity mode, dual 360° nozzles, and warm + cool mist. There’s also an aromatherapy slot where you put a pad and add essential oils, but the oils never touch the main water tank, which is good because that would be a cleaning nightmare. The control panel on the front has actual text labels (not just icons), which makes it easier to figure out what’s what without reading a manual.

The app side is pretty mature. You can see real-time humidity, set a target, adjust mist levels, switch between warm/cool, set schedules, and turn the screen off at night. There’s even a plant-care section if you’re into that, where it suggests settings based on the plants you pick. To be honest, that part is more gimmick for me, but the core stuff like scheduling and auto mode is genuinely useful. I ended up using the app way more than the physical buttons.

One thing to be aware of: this is not a filtered evaporative unit, it’s ultrasonic. That means if you use regular tap water and your water is hard, you’re going to get white dust on nearby surfaces over time. The included sponge helps a bit, but it’s not a real mineral filter. You really want distilled or RO water if you care about dust on furniture or electronics. That’s not unique to this model, but at this price, a better filtration option would’ve been nice.