Vornado Evap40 Evaporative Humidifier with Adjustable Humidistat, 4-Gallon Capacity for Large Room Coverage up to 1,000 sq ft, 3 Speed Settings, Easy to Clean Dual Tank

If you want a good reliable humidifier for your space this is the one to buy. I wanted an evaporative humidifier for a number of reasons: they don't produce a residue like the ultrasonic humidifiers and cool/warm mist humidifiers can. They won't over-humidify a space like the other types can -- air will only take on as much humidity as it can hold, and evaporation slows the closer the air gets its potential saturation level. And to ensure that over-humidification doesn't happen this humidifier also features a humidistat that will switch the unit off if the humidity exceeds the level where you set it. I bought my Vornado three years ago because it's such a simple design. The top fan unit, 2 water supply jugs, the reservoir pan, and wicks. Nothing fancy at all, just like the best evaporative humidifiers I've used in the past. As far as I'm concerned the simpler the design the less chance of something breaking. At the lowest two fan speeds the unit makes hardly any noise. Even the highest fan speed I don't think it is overly loud -- I sleep fine with it running in my bedroom. My recommendations for this humidifier: Purchase a humidity meter to monitor the levels in the room so you can better dial-in the Vornado's humidistat to your preference. Use distilled water. You don't have to, the humidifier works fine with regular tap water. But in the long run distilled water will give much better and consistent results. Have at least one if not two new wick sets sitting in reserve. That way when you have to replace them you can do so right away, then order another replacement. To combat/prevent bacterial growth -- use copper. Don't waste money on additives to combat bacteria. Copper works great as an antimicrobial and keeps bacterial growth in check (that is, zero). Preferably copper mesh (usually available through garden stores), but pennies will work fine (wash them clean before using them). The problem with pennies is, over time, the copper plating will get 'used up' and then it'll be the zinc core exposed to the water (this took about a year when I first used them). Zinc is supposedly antimicrobial as well, but I didn't want to chance it, and copper-less pennies look disgusting :) . I have a six-inch strip of copper mesh in each water jug. I have never had issues with bacterial growth in the jugs nor in the reservoir nor on the wicks while using copper as an antimicrobial. Regularly clean your Vornado, including vacuuming off any accumulated dust. Be especially diligent if you use only tap water and not distilled water because limescale will accumulate in the pan and on the outer surfaces of the water jugs. I run mine 24/7, except when its humidistat setting shuts it down or while cleaning the unit. The humidistat is sort of finicky, it's not really "exact" so much as the best way to set it is if the room is too humid, turn the humidistat until the unit powers down, then wait. I realized I had to finesse the setting over a period of days, fiddling between shutting down and turning on, until I got it set just right. Once I did get it dialed in I never had to worry about it again. I recommend purchasing a humidity monitor if you really want to watch those levels. For those first three years I used tap water, which works fine. However my tap water has a high mineral content, which means the evaporative wicks harden with limescale rather quickly -- as in a matter of days. At first I was rotating wicks once a week -- I'd have one pair of wicks working, then swap it out and soak the wick in vinegar water to disperse the minerals, rinse it out, then swap it back in the following week while I de-scaled the second wick pair. Problem is, over time, the wicks deteriorate from the vinegar soak cycles. As in they start falling apart. They re-mineralize quicker the older they get. And the ability to control mineralization continues to deteriorate over time. I purchased new wicks every three months just to keep up with the deterioration. I finally decided to switch to distilled water. The humidifier uses about 2 gallons of water a day so purchasing distilled water off-the-shelf is not an option, that's too expensive. I purchased a home distiller and distill 2 gallons of water a day. I also purchased an empty 2.5 gallon jug to have 2 gallons of distilled water ready for when one of the Vornado jugs empties. I fill the Vornado jug, then distill more water into the 2.5 gallon jug. Sure, it's a little extra work, but the benefits outweigh the inconvenience. One month after the switch to distilled water the humidifier wicks have remained supple, they are not mineralizing at all. To be honest I'm not sure when I'm going to have to replace the wicks, I've been running the same filter set for a month and they're doing great. I'm sure, over time, I'll figure it out. Already I can see I'm on track to saving a lot of $$ not having to replace two pairs of wicks every three months. Home-distilled water is a lot cheaper than purchasing it off-the-shelf. It is definitely worth the added cost to purchase a small home distiller. I know my distiller will pay for itself in less than a year compared to what I was paying for replacement wicks and vinegar. I am on my second Vornado EVAP40. The first one died after three years of constant use. The power-cord wire corroded with oxidation inside the unit which increased the resistance on the AC wire until it cooked its insulation and the unit quit working. I contacted Vornado customer service and explained the situation. I sent them the pictures they requested. Vornado honored their 5-year warranty and sent me a brand-new unit. Vornado is amazing and stands by their product, I have nothing but good things to say about them, their customer service, and this humidifier. If my unit had been out of warranty I would have purchased another one anyhow because it is that good compared to all the other humidifiers I've tried over the years.

This vornado humidifier is truly a life saver. I had a levoit tower $150 humidifier that didn't make a dent in my extremely dry room. We have old radiator heating and a lot of exposed pipes and it gets extremely dry 20% humidity dry. For some reason the dryness was worse this year and I was struggling to breathe, wheezing, I couldn't get my Levoit humidifier to go above 30%-35% even running 24/7 on the highest setting. I decided to try an evaporative humidifier and after a few days of research settled on this one because of the fan and I thought it would reach a better range with my tall ceilings. Within a few hours of using it got my humidity up by 25%. I finally was reaching comfortable levels of humidity and could breathe like normal. I use distilled water as I have a water distilled machine, totally worth it, I haven't had to change the filters yet or dealt with any grossness. I fill 2 gallons at a time usually, and if I want to use less for a shorter amount of time I usually just fill one side instead of both. There is a learning curve to get the containers on without spilling. Instinctively we want to go slow especially because it's full of water, but you have to just lay the containers down on the grove and quickly put them in in one fast movement. Don't need to use force just go quick otherwise water will spill. Once I realized that I haven't spilled it at all or had any leaking issues. I keep it running once the water is done to dry out and dry the wicks. It does make a "glug glug" noise every few hours depending on how high you're running it but I don't think it's loud or bothersome, I barely noticed it at first. The fan sounds like a fan, not sure why it seems people expect it to be quiet, any fan on max is going to make some noise, it's no louder than any other fan I have really. It's not quiet but I don't think it's unreasonably loud, could take some getting used to if you're sensitive to these types of sounds. There was a smell initially, it was off-putting but I was prepared based on reviews. It was the wicks not the decide itself so think it's unavoidable with any wicks. It took a few days to go away but eventually did completely. I'm impressed and surprised by the simplicity of the whole thing really. I'm used to the Levoits that's a bunch of pieces and is a pain to clean, this thing is really simple but functions great. I'm so glad I made the switch. No hate on the Levoit it wasn't the only humidifier I've had but was the fanciest most expensive one and I definitely had higher hopes and expectations for it. Thankfully, this one succeeded where the other failed Photos are 1) the humidity level in my room after this current humidifier was off for a few hours when I wasn't home 2) humidity level within 2 hours of turning on the vornado humidifier 3) my Levoit humidifier, and even when it was running for hours on high I couldn't get above 34% humidity at most

Before I review this product I feel it is important to differentiate the three different types of humidifier. Important note, all 3 types will have the occasional "glug glug glug" sound as water empties from the tank into the humidifier unit. - First, the Cool Mist. These use high-frequency sound vibrations to create a very fine water mist. The mist these emit is cool, and they are very quiet. They have no fan so slight hum is typically all you hear. They can end up leaving moisture on their surroundings, the cool mist does not just disappear up into the room but often will partially settle back down onto the table, floor, etc... It won't be dripping wet, but you need to be aware of this potential moisture issue. You'll need a source of air circulation to evenly humidify an entire room with this type. These require no filters or other consumables, use of mineral absorbing gadgets in the water is often mentioned but not required. They can be a real pain to clean depending on how many corners, nooks, and crannies were designed into the unit. Filling the unit with vinegar water for a soak will simplify things. The main drawback to these is the ultra fine white dust that gets on everything, everywhere. All the minerals in your water will end up in the air, and then in your closets, drawers, and cabinets, and on every surface everywhere. - Second, the Warm Mist. These use a mini hot plate to boil the water and emit a cloud of steam. It will be warm to hot if you stick your hand in it. Not only do they humidify but they can also cause minimal increases in room temperature. They also have no fan and run fairly quiet, but a little noisier than the ultrasonic Cool Mist type. Again, you'll need a source of air circulation to evenly humidify an entire room with this type. These also require no filters, but many will need small, inexpensive pads to absorb the minerals in the water which helps prevent them from solidifying into a layer over the heating plate. These units can be ridiculously difficult to clean depending on the design, and care must be taken to not scratch up the heat plate. - Third, the Evaporative humidifier. These have large wicks which soak up water, and a fan pulls air through the wicks, evaporating some of the water, then sends the humidified air out into the room, These emit no mist or cloud of steam. Given the fact that they have a fan they are a little noisier than the other two types, but they will humidify the entire room a lot better and quicker than the other 2 types because of the air circulation. Typically these are easy to clean if done regularly although this depends in large part on what's in your water. Also, this type uses wicks which will have to be replaced at regular intervals determined by the mineral content of your water. They go for around $10-$15, so be aware there are continuing costs if you use this type of humidifier. This unit is an Evaporative type, and it works quite well. Here in the Pennsylvania winter it easily keeps a large bedroom with attached sitting room at 50% humidity on the medium fan setting with the humidity control set between half and two thirds. It will run for a 2-3 days (sometimes more) without needing a refill due to the large tanks, which is phenomenal compared to other units I've tried. Refilling is super easy since there are no caps or valves. Fan noise is minimal on medium setting, almost imperceptible on the low setting unless you are in a very, very quiet setting or have it placed unnecessarily close to your bed. The occasional "glug glug glug" of the tank refilling the chamber is louder than the fan unless you're using the high fan setting. As of the date of this review it has been up and running for 7 weeks and I have not yet needed to replace the wicks. I have flipped them once, that's it. Overall I am very happy with how this unit performs, but there are a couple negatives. First, the humidity control is wildly inaccurate on mine. One day it will be shutting off when the room is at 42% humidity, a couple days later it will still be running when the room is at 60% humidity. That's a big difference, going from easy breathing to rain forest without touching the settings. Keep a separate inexpensive humidity meter in the room to accurately gauge the humidity and make adjustments to the settings as necessary. Second negative, the price. This thing is outrageously expensive given the complete lack of technology inside it. There's a 4 position on/off/fan speed rotary switch, a dial for the inaccurate humidity setting, and a fan. No touch screen controls, in fact no screen of any kind. No fancy digital controls, no bells or whistles, we're talking 1970s tech if not earlier so the comparatively high price is really unjustified. Also, the product page claims in two different places that this unit "senses how much humidity and circulation is needed to maintain your ideal environment and makes adjustments automatically." I have yet to hear this thing vary the fan speed, so I'd have to say it is not sensing and/or responding to the need for more air circulation, or less for that matter. I've no idea what adjustments it is supposed to be making, and the included manual makes no mention of this ability. It turns on, or off, when the supposedly appropriate humidity level has been reached. That's it. I'd have to rate this claim as false. Overall it's a highly effective unit, fairly quiet, easy to fill, easy to clean, with minimal costs for consumables. I'd recommend it.

I've been using this humidifier seven years to keep my musical instruments happy. I struggle to remember the humidifiers I owned prior to the EVAP40 but I recall being frustrated. The EVAP40 was recommended on a musician forum so I decided to give it a try. I really like the design of the EVAP40. It has a large water capacity which is easy to refill. It's easy to take apart and clean. The Low fan setting is pretty quiet. I usually run mine on Medium or High which don't exactly purr like Low but with the health of my instruments at stake I don't mess around. I don't mind the occasional gurgling sound as water flows from the tanks into the base. To me it's a reassuring sound that lets me know it's working. I usually get a month or so out of a set of filters using our tap water which is pretty hard. I don't bother cleaning the filters with vinegar and getting a second use out of them. I chunk 'em and put in a fresh set which isn't exactly cheap but frees up time I can be doing something else. I keep at least three sets on hand in case there's a shortage but so far I haven't had trouble getting them. Vornado usually has a filter sale once a year and I've taken advantage of that a few times. The only feature of the EVAP40 that I have mixed feelings about is the humidistat control. I like the simplicity of the design and it works well for the most part but sometimes it doesn't do what I expect and humidity gets too high or too low and I have to tweak the setting again. A digital humidistat would be nice but also something that could get wonky and break. I've learned to live with the way the EVAP40 works and overall I'm happy with it. I've been running the EVAP40 for seven years and so far haven't seen the need to shop for a replacement. I probably won't look for one until this one dies which might be a while.

My biggest gripe about this thing is that the build quality does not live up to Vornado's standards considering the price. The housing is cheap, thin, sharp-edged plastic (not sure what kind) and the jugs are HDPE - the same stuff they make milk jugs out of. They do not have any kind of valve, only an open spout. You basically have to drop the jugs into place to avoid spilling everywhere, which is especially annoying when each one is full of 15 pounds of water. Filling them is a royal pain in the ass since the spouts are very small. You either have to fill them under a sink faucet (which gets them about halfway full in my case due to the angle) or hold them up to a halfway-on bathtub faucet for two straight minutes (which, again, 15 pounds). Your only way to remove them is to grab onto the slight bulge molded into the top, which is completely useless when it has water in it. The amount of water it puts into the air is satisfactory. I've found that it goes through four gallons of water in about 36 hours on high in room temperature, low-to-moderate humidity air. One gallon of water is plenty to run it on high overnight. It is noisy but tolerable on high, acceptable on medium, and whisper-quiet on low. The noise isn't particularly unpleasant, just loud on high. The humidistat is basically useless. As some other reviews have noted, it is wildly inaccurate. I wish they had just left it out and dropped the price five bucks. That, or replace it with something that actually works. I just crank it to the max and pretend it doesn't exist. As a brute force humidifier, it does the job. It just happens to be the cheapest-feeling, ugliest Vornado product I've ever owned.

This is a great humidifier. I understand many other reviews think otherwise and this product has, surprisingly, a somewhat low score of about 3/5 stars. However, for my wife and I, this has been a blessing and a great addition to our apartment. I researched extensively online, trying to find the best humidifier that would increase the humidity to quite a high level which for us is 70% relative humidity in a 700 square foot apartment. I know, that's really high and people caution to raise the humidity so high that mold may grow. We have only seen one sign of the high humidity causing harm to anything in our apartment, which is our screwdriver rusting while sitting in the open air rather than in a sealed container. We stuck the screwdriver in a Tupperware container and it prevented any further rust from the very humid air. For my wife, high humidity really really helps her skin to not be so dry, as she has severe eczema aka dry skin/itching/cracking skin. She could not sleep without the humidifier some nights and stayed up itching all night while drifting back and forth from sleep, of course not letting her rest properly and therefore further making her eczema worse. Using this humidifier helped her a lot and her skin has started to heal more, closing her open wounds and his skin being softer and she feels less dry and itchy. I am so happy we bought this and so grateful this humidifier works well, seriously. For us, this changed my wife's life for the better. The humidifier wicks are easily replaced and for us, running the humidifier on high 24/7, the wicks last 3-4 weeks, when about halfway up the wick you can see yellow crusty material. The humidifier does not increase the humidity as well at around 3 weeks and replacing the wicks with new wicks usually increases the humidity by about 5% relative humidity, compared to the 3 week old wicks. Lastly, we actually are using two of these Vornado Evap40 humidifiers in our apartment, to increase the humidity even more, to our desired level of ~70% relative humidity. We were using only one of the humidifiers in the fall and the humidity did reach 65 - 70% normally. We live in Mobile, Alabama for reference, which usually has quite high humidity normally. However, when it changed to more "winter" weather here in Alabama, in November, the humidity in the outside air decreased and therefore the humidity also decreased in our apartment. The humidity was about 45 - 50% using one humidifier in the month of November. We wanted to try using another humidifier and see if that helped raise the humidity; we bought another and now using two humidifiers in November in Mobile, Alabama has increased the humidity to 70 - 75%, quite a lot. Overall, I think this a great humidifier. It accomplishes what you would desire, to raise the relative humidity in an enclosed space, by about 10 - 20% using one humidifier, in a 700 square foot space. The humidifier is "relatively" quite on the highest fan speed, probably making 10 - 15 decibels of sound, like a somewhat gentle room fan. I think it is actually a comforting white noise, and definitely not too loud to talk over, as my wife and I have conversations easily in our normal voices with the humidifier right next to us. Try this humidifier and always if you don't like it, you can return it.

This review contains an original and a revised posting. The original rating was 4. The revised rating is 1. The original post: These things work pretty well, but they run through more filters than a chain smoker, and replacement filters are absurdly expensive. Pros: it works, disassembles nicely for cleaning, comes with two huge holding tanks, has a stylish contemporary look. Cons: must run on high speed for good evaporative output, high speed is disturbingly loud, you'll need lots of filters unless you have pure water and nobody has pure water unless they distill it, expensive filters. Disclosure: I just bought my second unit. It seems essentially unchanged from the old unit. Haven't hooked it up yet. Hope it's quieter. The old unit is still running but threatens to die every day. It's given 5+ yrs of service, but even when new was too loud for bedroom use. The revised post: 2/27/24 The old unit finally died (the motor), so I unboxed the new unit. It looked much like the old one so I expected no problems operating it. I filled both tanks with water and inverted the first. As you may know, when the tank is inverted water flows into the holding tray until it is about half full, then the water stops. On my old unit the water flowed in with a familiar "glub glug" sound, but on this new unit the sound was missing. Instead, the water rushed into the holding tray. And rushed, and rushed, and ... rushed some more. Until it came streaming over the top of the holding tray. And then it just kept on coming. As I looked on incredulously it spilled in seconds onto my bookcase, down its sides, down its front and back and onto the floor. I snatched off the tank and examined it. It seemed absolutely normal. No holes, no malformations, no sign of mistreatment. I refilled it and tried it on the opposite side of the unit. Only to flood the floor again. By now the corner of my office was a swamp. I moved everything to the garage and repeated the experience two more times, successfully flooding my work bench and everything in its vicinity. I felt compelled to get to the bottom of the mystery. I discovered that one tank works perfectly, when loaded onto either side of the unit, and it even has the old familiar "glug, glug" sound effect as it feeds in the water. The other tank, however, is a complete disaster. It forcefully flushes its contents into the holding tray until the tray fills and then it keeps flushing, forcing water over the top edges of the open holding tray, creating an absolute disaster of a mess. I'll make a video of the flooding process and post it in case anyone thinks I'm making up any part of this deplorable story.

Very easy to use and clean. There are four pieces to this unit not including filters: base bottom, base top(motor/fan portion), two water tanks. It seems very basic and simple, yet it works very well. The tanks can be removed and refilled while the machine is running. The tanks are made to be carried with ease and balance well on the counter/sink while filling. There's a lip on the tank to catch the side of the base so you line up the lip and just tip the tank in place. It's easier to tip a full 2 gallon tank into place than it is to pour milk from a full gallon container. There are two filters/wicks with the unit, and replacements are currently about $12 for a 2 pack, which I find reasonable. Sometimes the top of the wick is dry and/or slightly orange, so I flip them. I read about and tried soaking in vinegar + water then rinsing and that takes the orange right out. We've left this on 24 hours a day for about 10 days so far and the house went from ~10% humidity to 36-44% humidity. This covers about 1,000 sqft and I have that on each of two floors. I set the machine by the stairs in the middle of the house and it helps significantly with air flow between the floors. I knew going in this was only meant to humidify half my space. I'm pleased it's doing such a great job keeping both floors of my desert home close to 40%. One aspect I didn't expect is the particular sound frequency the machine emits. I'm very sensitive to sounds. Most fans are at a frequency that really bothers me, so I can't have them running for very long. This Vornado is at a frequency that doesn't seem to bother me. Working all day just 6 feet away from it on high and the sound is there but it's more like white noise or something. At night we can barely hear it running in the other room, and it doesn't keep us awake. We tried leaving a fan in the same location a while back and the sound was so annoying it had to be turned out before we fell asleep. I'm not sure if this aspect is intentional, but it's perfect in our case. To clean you just use some bleach water. There are no hidden crevasses. While I don't anticipate the need to scrub crud out of the tanks, I'm sure a healthy hot water + bleach shake would do the trick if needed. The two things to watch for are putting the base top onto the base bottom. You need to line it up and I suspect if you aren't careful and try to jam it together the plastic might chip fairly easily. The other is moving it. Take off the tanks to move. Otherwise, as you move the machine the tanks sense the water level changing and more water flows into the base, which then flows onto the floor. I leave the base top on about half the time when moving, but you basically have a tray of water and we all know that trays of water spill very easily if the water starts moving back and forth. Finally, this thing is amazing for moving air around. It's very efficient and cools down my second floor by a few degrees simply by moving the air. Highly recommend.

Humidificador lo estaba utilizando en mi recámara. Los resultados fueron muy malos. Terminé regalándolo.

There is really no assembly. After you remove the packaging it is already assembled in the box. Because it is evaporative rather than cool mist, it does a much better job, and no risk of white deposits all over your furniture. Filling is easy, and I have been running it continuously with only the need to fill one of the two tanks daily. It preferentially depletes one tank before starting on the other. There is a fan, so there is some noise, but it’s white noise and I don’t notice it. (Same level of noise as my Honeywell air purifier.) It is twice the size of a cool mist humidifier, so it is about as big as anyone would stand for as a tabletop item. But, being evaporative, it does not need to produce a directed stream, so you can actually put it anywhere and get the health effect you need. My only (minor) issue is that the construction means that all four sides need to be about 6 to 12 inches from a wall in order to permit filling and proper air circulation without having to be constantly moving it. I love this thing.

I did a lot of research before replacing my 4 year old dead humidifier. I find it very annoying that things are built to fail after the warranty is up. We love our Vornado humidifier. No LEDs to fizzle out after a year. No lugging jugs of water to pour down a spout. This product is easy to use and easy to clean. It is far quieter than our last dud. I love the two large containers that are easy to remove and fill. We have no trouble placing the containers back in, no spilling. It does glug now and then. A non issue for us. The fan is quiet. On the first level I can hardly hear the fan. On the third setting the fan is noticeable but not interfering with the T.V. or conversations. Also the wicks (filters) aren't expensive to replace. This humidifier is far and above our favorite. Love it!

I've been using mine for about 6 months now in my apartment & it works great. The simple yet smart design makes cleaning & maintenance a breeze. You don't have to worry about what's in the water ending up in your air like ultrasonic humidifiers & there's no heat/steam/condensation like you get with older evaporative designs. For the first day or two of use, it might seem like it's running constantly as it builds up humidity. Afterwards (depending on weather) it runs about half the day to hardly at all. If, after a few months of use, it seems like it's running more than usual, it's probably time to replace the wicks as they become saturated with mineral deposits. On that note, the wick replacement is the main downside to this design, however it's not a huge expense. From the one replacement pack I've had to buy so far, I estimate the cost of wicks to be roughly $7🇨🇦 a month. This will probably vary depending on your water hardness. My tap water has very high mineral content so I need to replace mine a little more often (once every 2.5 months). Also there's no digital display, only a knob that doesn't show % humidity. There's a good digital monitor on here from Thermopro which is relatively inexpensive that I'd also recommend. I subtracted 1 star just for these added expenses but in terms of functionality I give it 5/5.

This thing is so much more effective than my last evaporative humidifier it's not even funny. On full blast, within minutes a hygrometer in the same room showed the humidity creeping up from 12%. This can bring my whole one bedroom apartment from 10-15% up to 35% and hold it there, while the Honeywell unit had a problem getting just one room to 30%. This might be good for one floor of a smaller house, or any one room, but you may want a large whole-home unit if you want more than that. Perfect for a highrise condo/apartment though. I think the effectiveness is down to the design. It has a good ducted fan (Vornado's specialty) that is very effective at pulling in air / creating negative pressure inside the housing, and the two big wicks give a lot of surface area for evaporation while probably also slowing airflow just enough to help with that pressure. It has a built-in humidistat. It seems to work OK, but you might have to manually manage it sometimes to keep it from going too high or low. It's enough to leave it untended most of the time though. The review saying that a cloth left on top of this stayed dry is... that's not a reasonable way to measure a humidifier's efficacy. Only an ultrasonic humidifier, which atomizes the water and so just acts like a continuous spray bottle, would actually have the effect of wetting that. The proper way to measure a humidifier is to use a hygrometer to measure your room's humidity. (Ultrasonic humidifiers throw tiny particles of water into the air, so they significantly degrade air quality unless they're used with pure water. They're not great. This humidifier doesn't make a nice pretty mist effect but it also doesn't make you breath in calcium, silicates, and other minerals) The photo is from a cold day, humidity in here would normally be 17% at most. Clearly the humidifier works and makes the air wetter. Of course it doesn't actually make sense to measure on top of the humidifier directly like this.