Humidifiers vs. Diffusers | Pros & Cons of Each

| Last Updated: April 9, 2021

When winter hits, we focus on keeping warm and avoiding sniffles. We also shift our schedules to spend more time indoors, close to our central heating units. We forget that lower temperatures limit the amount of moisture in the air, drying out our skin, hair, and respiratory tracts. And when we get into buildings and shed our winter layers onto coat racks, we under-estimate the drying effect of our heating systems.

Already, our HVAC is working with cool, low-moisture air from outside. Once that drier air comes inside and gets warmed up, its limited moisture spreads over a wider area, meaning indoor humidity drops to 20%. (The ideal is between 40% and 60%). This dip has major health consequences, so it’s a good idea to push those humidity levels back up.

Humidifiers and diffusers are both good ways of doing that, and many consumers get them confused. So what is the difference? Read on to find out more about these product types.

Humidifiers vs. Diffusers Comparison Chart

  • Releases Either Cool or Warm Mist
  • Has a Water Tank Capacity of 1.58 Gallons
  • 1-Year Warranty With a Free Extension to 2 Years
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  • Doubles as a Diffuser for Added Value
  • Humidifies an Area of 256 to 323 Square Feet
  • 45-Day Money-Back Guarantee + 12-Month Warranty
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  • Doubles as a Humidifier and a Diffuser
  • Shuts Off Automatically if it Has No Water
  • Whisper-Quiet Thanks to its Ultrasonic Technology
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  • Low to No Noise During Operation
  • Can Run Non-Stop for 5 to 10 Hours
  • Looks Gorgeous on Your Counters and Nightstands
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  • Works Continuously for Up to 6 Hours
  • Multiple Light, Mist, and Flow Settings
  • Cycles Through 7 Soothing LED Shades
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What is a Humidifier?

A humidifier is a device that raises humidity levels by gradually releasing moisture into your living space. This moisture could be warm or cold, depending on your needs. Cool mist gadgets are safer for homes with young ones, because the machine stays cold throughout. Warm mist devices use heat to create moisture, so the surface of the gadget gets hot.

The heat generated by the warm mist devices means if a child or pet accidentally touches it or plays with it, they could hurt themselves. It’s a real risk because the colorful designs and attractive shapes of typical humidifiers are a beacon for curious pets and toddlers. Some humidifiers are capable of releasing both warm and cold air, depending on your settings. It’s a helpful option because it’s more versatile.

Ordinarily, warm mist humidifiers work by heating water to the boiling point, then pushing the steam into the room. With cool mist humidifiers, there are two main techniques. The first is to use rotary fan blades to suck air into the machine, pass through a wick soaked in water, then push the wetter air back out. The second is to pour water onto a vibrating plate that oscillates at ultrasonic frequencies, atomizing water into a mist which is then pushed out.

Because humidifiers are water-based, they don’t necessarily do well with additives. Some brands and models allow you to drip scented oils into your device, but most humidifiers can get clogged and damaged if you add oil to the water. Others have a designated chamber where you can deposit oil-infused pads formulated for that particular product. So even if you do have a humidifier that takes oils, read the instructions carefully to avoid inadvertent damage.

What is a Diffuser?

Essential oils are thought to have different properties. Some can be soothing and medicinal. Others are enticing and stimulating. If you are a proponent of their properties, then a diffuser is a helpful tech tool. It releases moisture into your home or office, but this moisture is laced with oils and scents. Usually, oil and water don’t mix, because they have different densities. Diffusers are designed to merge these two liquids, allowing consumers to enjoy their combined effect.

Not all diffusers use water though. Some just rely on essential oils, disseminated via a fan. That said, there are different kinds of diffusers, and many of them mimic humidifiers. The four common kinds are evaporative, ultrasonic, heat-based, and nebulizing.

Evaporative diffusers are designed like humidifiers. They have a special pad where you drip the recommended amount of oil. The gadget’s fans blow onto the filter, evaporating your oil and releasing it into the air.

Heat diffusers work the same way, but instead of the oil being evaporated by fans, the oil is heated to turn it into vapor, then it’s released into the room.

Nebulizers are a little more complex. Rather than a pad, oil is poured into a tube. When air blows across the tube, it creates a vacuum, pulling the oil to the top of the tube. As the air keeps blowing, the oil begins to evaporate and spread its fumes to the rest of the room. This process can get loud.

Finally, ultrasonic diffusers are loaded with water mixed with essential oil. The disc at the bottom of the diffusion chamber vibrates to atomize the liquid, turning it into fine, scented, misty particles, which are then pushed out of the diffuser and into the room. This process produces a trickling, gurgling sound that some find soothing (and others deem annoying).

Humidifiers vs. Diffusers - Similarities and Differences

Both humidifiers and diffusers work by releasing moisture into the air. It could be in the form of steam or mist and is visible for a few minutes before it dissipates. You might not physically notice the difference unless the moist air released by your device is scented. So how exactly do you distinguish one from the other, and how can you be sure which one is right for you?

Humidifiers vs. Diffusers - Differences

To a novice, these devices are easy to mix up, and they seem to perform similar functions. What’s distinct about each device and are there reasons to pick one over the other?


The ‘fuel’ used in diffusers and humidifies varies. A humidifier may use anything from half a gallon to six liters.

Diffusers (or humidifiers with essential oil slots) only use a drop or two of oil, though some versions (like ultrasonic diffusers) are loaded with water as well as oil.

Air Quality

Your typical humidifier has filters built in, to make your air more breathable.

Diffusers aren’t generally equipped with filters, so if you’d like your air purified, but you still want to use healing oils, pick a gadget with filtration units attached.


For the most part, humidifiers use plain water. Ideally, distilled, to minimize white dust. If your humidifier works with oil, there might be a slight scent.

Diffusers, on the other hand, are all about the flavor, so their scented essential oil additives are easy to spot. That’s the whole point.

Healing Properties

If you have a cold, allergies, or itchy skin, a humidifier can unblock your air passages, moisturize your tissues, and relieve stuffiness.

Diffusers have the addition of specific oils, so it can be therapeutic – physically, emotionally, and psychologically.

Mood Influencers

Adding humidity to your bedroom or living room can make you more comfortable. You won’t feel as stuffy or scratchy and that could affect your spirits. That said, it’s just water.

Diffusers have a stronger effect on your mood, whether it’s sensual jasmine or uplifting orange oil.

Humidifiers vs. Diffusers - Similarities

These two ‘steamers’ and ‘misters’ have a lot in common, Some models even straddle the line, performing both functions. This makes your purchasing position even more complex. Still, what do these two device categories have in common?

Moisture Control

Humidifiers and diffusers both pump extra moisture into the air, whether it’s water, oil, or a mingled blend of both. This makes them great for your skin, reduces pet dander, and enlivens house plants. Unfortunately, the added moisture means both devices can accumulate condensed moisture on your floors, desks, and other surfaces.

Disinfecting Traits

Raising the temperature and moisture in a room is a good way to beat certain bacteria. Both diffusers and humidifiers make your environment less welcoming to germs. Plus, versions that have built-in filters can help you trap some of those malevolent micro-organisms.

Access to Devices

Humidifiers and diffusers fall under the same broad category of HVAC devices. So your favorite brand probably produces both. And if you’re shopping, they’ll be in the same stores, or at least the same section, of the store. Double-check to be sure which one you’re buying.

First Aid Options

If you wake up in the middle of the night and you have difficulty breathing, or if you notice you’re scratching yourself raw, both gadgets can offer temporary relief as you troubleshoot the source of the problem. It’s especially helpful for kids, because as a panicked parent, you may not differentiate a coughing fit from dust/dander inhalation versus an attack of undiagnosed asthma.

Basic Design

The shapes, sizes, and specifications of these two gadgets are vast, but they have many shared features. These could include:

  • A nozzle to let out the moisture and/or scented oil
  • A tank to contain the relevant liquid
  • A wick, disc, or heating device, depending on desired results
  • An indicator to show when it’s time for a refill
  • A broader base to prevent the gadget from tipping over and causing spills

Our Favorite Humidifiers

Ideally, you want a device that works fast, doesn’t make too much noise, and helps you determine the best humidity level for your current situation. Built-in humidistats are helpful. If possible, find one that shuts itself off to prevent accidents. Let’s explore our top selections.

LEVOIT Humidifiers for Large Room Bedroom (6L), Warm and Cool Mist Ultrasonic Air Vaporizer for Home Whole House Babies, Customized Humidity, Remote Control, Whisper-Quiet (White)


  • Works Safely With Aromatic Oils
  • Faster Moisture Release at 500ml Per Hour
  • Two Control Options: Touch-Panel and Remote
  • Two Independent Nozzles That Both Rotate 360º


  • Weekly Cleaning Process is Complex and Drawn Out

Our Review

Versatility is everything when you’re shopping for electrical appliances, and versatile is this Levoit humidifier’s middle name. It goes double all the way, with two moisture temperatures, two separate nozzles, two control modes, and two co-dependent liquids. The latter claim is relative because the liquids don’t actually mix. Instead, you drizzle oil on the aromatic pad, and it’s the fumes that end up mingling with mist or steam.

With two of everything, it can be tough deciding what features to activate and which ones to leave alone. That’s what auto-mode is for. The humidifier displays your room’s actual humidity, then pre-sets itself accordingly and goes to work. You only need to step in when the water level goes below 480ml. That said, Levoit has been known to wet floors, so it’s best positioned on a desk or some other raised surface. Especially if you leave it on for the full 20 to 36 hours.

One of its top selling points is its promise of moisturizing your space 25% faster than other models. This statistic depends on whether it’s in cool mode or warm mode. The humidifier releases cool mist at 300ml per hour, but that figure shoots to 500ml when you choose the warm mist option. The difference is driven by atmospheric temperature – warm air can hold more moisture than cold air, so the air that’s heated before it exits the humidifier will naturally contain more water particles. The tank itself is made from premium ABS, so you know it’ll last.

Bottom Line

This humidifier is packed with attractive features, from dual nozzles to dual mist selections. But unless you’re ready to dismantle and wash it every week, widen your shopping options.

Best Humidifier for the Money:
VicTsing Cool Mist Humidifier

VicTsing Essential Oil Diffuser, 300ml Oil Diffuser with 7 Color Lights and 4 Timer, Aromatherapy Diffuser with Auto Shut-off Function, Cool Mist Humidifier BPA-Free for Bedroom Home


  • Can Be Used With or Without Added Oil
  • Ultrasonic Technology Makes it Extra Quiet
  • Beautiful Design With Enhanced Aesthetics
  • Its Power Cable Tucks Discreetly Beneath the Device


  • Small Water Reservoir for a Humidifier – it’s Only 300ml

Our Review

The majority of humidifiers are incompatible with essential oils. And even for those that do accept oil, it’s not mixed into the water. Instead, it’s loaded into a designated compartment. The VicTsing humidifier does take oil, and it’s easy to use because you can drip the oil directly into the water reservoir.

The tank is deceptively small, but it can run up to eight hours continuously, and when the water is depleted, the humidifier waits five seconds, then shuts itself off automatically. This is a crucial feature because with the tank being so small, it’s easy for it to run out of water unnoticed.

However, you don’t have to wait for it to run dry. Instead, you can time it for an hour, three hours, or six hours, opting for light or heavy mist. It works slowly though, only releasing 25 – 30ml/h. It has seven colorful lights that can be turned on in automated sequence, lit one at a time, or shut off altogether. You can set the lights at bright or dim, so that’s 15 color options overall.

It displays a gentle line of light in the middle of the device, but light seeps out of the top spout too, offering a comforting nightlight. The humidifier itself has gorgeous wood grain patterns, and comes in light, deep, or redwood-brown. The gadget has two operating buttons – one for light and one for mist. It’s easy to fill and clean, because the top comes off completely, leaving a wide opening of 6.6 inches. Just make sure any oils you use are water-soluble to avoid damage.

Bottom Line

This humidifier is really pretty, and far more powerful than it looks. Its scent and soothing colors offer additional relaxation, but it’s a no-filter humidifier, so you do need to clean it every week. Luckily, its low-tech, wide-mouth design makes it easy to rinse and refill.

Honeywell HCM350B Germ Free Cool Mist Humidifer White


  • Ultraviolet Light Rays Kill Majority of Germs in the Water
  • Wider Tank Opening Means Fewer Spills When Filling and Cleaning
  • Keeps Wooden Furniture and Indoor Plants From Withering or Cracking
  • Maintains Humidity Levels Which Lower the Lifespan of Cold/Flu Viruses


  • Averse to Essential Oils

Our Review

This Honeywell product has ‘germ free’ in its name, and its manufacturers claim it can eliminate 99.9% bacteria. It’s not an empty promise, because the device is loaded with two separate filters. The first filter washes the air to remove larger particles, while the second layer has anti-microbial benefits, so it traps and kills virtually all airborne germs. The Honeywell HCM350W makes 30% less noise than competing products, and its tank is designed for quick refills.

Unlike other humidifiers where you have to pull off the entire top portion, the Honeywell’s tank is positioned at the side, offsetting the white device with a pretty blue accent. The top of the water tank has an easy-grip, hooked handle that you can easily yank out to fill or clean. Once full, the humidifier can operate continuously for up to 24 hours.

It’s an evaporative device, meaning it’s not possible to release too much moisture (and thus eliminates the need for a humidistat). Evaporative humidifiers work by pulling in the dry, surrounding air and feeding it through a water-saturated wick before releasing the now moist air back into the room. Inside the humidifier, air blows onto the wick to speed up evaporation, but the room itself can only hold so much moisture.

So once your air is sufficiently moist, your humidifier stays on, but it doesn’t release any more moisture into your living space. At that point, the air going into the humidifier has the same relative humidity as the air coming out of it. Unfortunately, the Honeywell doesn’t have auto-shut functionality, so it will continue to run and use up electricity even though it’s not offering an added benefit in terms of humidity.

Bottom Line

For sufficiently humid indoor spaces, the added benefit of ultraviolet water treatment, and detachable components you can clean in the dishwasher, take a dip into the Honeywell HCM 350W.

Our Favorite Diffusers

On a diffuser, the timer matters more than the auto-switch. This is because diffusers only hold a few milliliters of oil, so it’s harder to gauge when they need a refill. (And easier to forget to switch them off.) A built-in timer is, therefore, essential. That’s why our top picks all have one.

Essential Oil Diffuser Humidifier (300 ml) BPA Free Air Diffusers for Essential Oils - Light Therapy & Aromatherapy Diffuser Air Humidifier - Auto Shut Off with 4 Timer Settings & 7 Mood Color Lights


  • Diffuses Areas of 125 to 215 Square Feet
  • Humidifies Slightly Smaller Areas of 108 Square Feet
  • 7 Soothing LED Colors Including Pink, Yellow, and Purple
  • Light and Mist Work Independently so You Can Use One Without the Other


  • Its Plain, Minimalist Design Isn’t Very Decorative

Our Review

For diffusers, 300ml is a large capacity, though it’s tiny in the humidifier world. This can get a bit confusing, so it depends on which function is more important – the steam or the scent.

Still, even at this capacity, the diffuser can stay on for between eight and ten hours. Unlike humidifiers, diffusers don’t need to run 24/7, so you can use its timer to program it for an hour, three hours, or six hours. (Note that time markings on the device are listed in minutes: 60/180/360.)

It’s easy to use this diffuser because the oil mixes directly into the water. It’s an ultrasonic diffuser, so will operate with low noise and no heat. It’s a discreet device – it looks more like a storage canister than a diffuser. Its understated design is fine for a low-fuss home and perfect for conservative office use.

The one downside is operation. With only two buttons, it could take a while to figure out how to work it. For example, you press the ‘light’ button once for ‘on’, which lets the light change automatically. Press twice to pick a single color and a long-press for ‘off’.

Similarly, the mist button needs a two-second press to power up and a longer-press to turn it off. A double-tap sets the mist timer. When you want to clean your diffuser, dip a Q-tip in plain water or diluted detergent, then use it to wipe the disc oscillator (i.e. the vibrating plate). Also, note that this is a diffuser with humidifying functions, so its diffusion powers are stronger than its humidifying properties. It’s not your first choice as a humidifier.

Bottom Line

Many of us want devices that are pretty, especially if they’ll be displayed in public spots. This diffuser works beautifully, so if your style leans towards the utilitarian, it’s a good pick. Plus, the rotating colors add to its aesthetic appeal.

VicTsing Essential Oil Diffuser, 150ml Mini Wood Grain Aroma Diffuser, Aromatherapy Diffuser with Auto Shut-Off Function and 7 Color Lights BPA-free for Office Home Study Yoga Spa Baby (Dark Brown)


  • Suitable for Infants and Toddlers
  • Is a Lightweight Device (8.2 Ounces)
  • Offers 14 Delightful Lighting Options
  • The Whole Top Comes Off, so it’s Easy to Clean


  • Some Users Complain it Makes Their Surfaces Damp

Our Review

VicTsing is known for dual functionality devices, and you might wonder what distinguishes this diffuser from their humidifier. Well, it’s slightly smaller, at 4.5 by 5 inches (compared to the 5.7 by 6.6 inches of the humidifier) and it has half the capacity at 150ml. That’s on the larger side for a diffuser though.

The VicTsing diffuser covers 100 square feet and can run uninterrupted for five to eight hours in diffusion mode and six to ten hours in humidifying mode. You can turn it on untimed, or pre-set it for an hour or three.

Like its twin, it has seven colors that can be bright, low-lit, or turned off altogether. If its water tank empties during use, the diffuser shuts itself off without your intervention. It’s a good choice for aromatherapy because it emits emotive lights and scents with no disturbing noise. When its oscillator vibrates, it releases negative ions that are proven to shift your mood. It’s a quick way to relieve your home or office of unpleasant scents.

The gadget is certified BPA-free, making it safe for babies and acceptable for wellness centers and yoga studios. Be careful when you fill your diffuser because exceeding the limit can spoil the device and cause leaks. Also, it doesn’t include a measuring cup, so keep a close eye on the max line. It releases cool mist, but the water warms a little while the device is on, so don’t panic. Also, before you add any oil, read its label to be sure it’s soluble in water. Otherwise, it will float at the top of the water tank and end up spoiling your diffuser.

Bottom Line

For portability and aesthetics, the VicTsing diffuser is a good choice. Just be sure you don’t mix them up and buy a VicTsing humidifier instead, since they look similar and both offer dual functionality. Also, be ready to clean it every week.

Best Diffuser for the Money:
URPOWER 2nd Version Essential Oil Diffuser

URPOWER 2nd Version Essential Oil Diffuser,Aroma Essential Oil Cool Mist Humidifier with Adjustable Mist Mode,Waterless Auto Shut-Off and 7 Color Lights Changing for Home Office Baby


  • Whisper-Quiet for Overnight Use
  • Made of Hard Polypropylene (PP) Plastic
  • Can Release Mist Continuously or Intermittently
  • Has an Auto Shut-Off Function in Case the Water Dries


  • The Oils Are Not Included so You Have to Budget for Them Separately

Our Review

You might want a diffuser to keep you sharp while you’re studying, in which case you’d load it with cognitive enhancement oils like lemon, peppermint, orange, or rosemary. These are thought to boost your memory and concentration.

In addition to working well with these oils,  the URPOWER diffuser is silent, so it won’t disrupt or distract. It has a 100ml capacity, and if you want it to release steam non-stop, it will run for three hours, showing a red indicator light.

On the other hand, you can set it to release intermittent mist that spurts every 30 seconds, turning the light green and doubling its run-time. The red/green indicator light doesn’t affect the seven LED colors – they’re separate functions.

When you want to clean the diffuser, unscrew the top, pour in a little water, and swish it around with a soft brush. Pour the water out carefully to avoid wetting the air outlet. Tilt the diffuser away from the outlet, so that the water slips out the other side of the device – i.e. the side that doesn’t have an air outlet.

You might wonder how exactly this diffuser produces cool mist when it clearly has a heating element. The water gets hot, causing the essential oils to evaporate and release fumes. But before these fumes exit the device, they’re passed through a cooling coil.

In this way, the diffuser can emit the scent into the room without raising its temperature or potentially scalding anyone. Avoid touching the ultrasonic oscillator directly – it’s quite sensitive. Tap water works fine with this diffuser and the oils aren’t included. Be sure not to overfill the tank beyond the max fill line.

Bottom Line

When you’re looking for something cute, low-fuss, and versatile, URPOWER is it. The oil can be added directly into the water, and the LED light show is a nice touch. But you have to be careful while you clean it, because it’s easy to drip liquid into the air hole, ruining the device completely.

Top Pick Between Humidifiers and Diffusers

At a glance, it’ll be tough to know whether that steaming, gurgling device is a humidifier or a diffuser, at least in someone else’s house. In your own, your decision is driven by several factors. Are your residents sensitive to scent? If they are, you’re better opting for a plain water humidifier. Get one that can’t accept essential oils – if only to reduce temptation. Humidifiers are also preferred if your primary problem is lack of indoor moisture.

On the other hand, if you want to change the way your room smells, or if you’re feeling nostalgic for a particular flavor, then you need a diffuser loaded with the right essential oil. Aromatherapy doesn’t work as well with humidifiers, even in models that can survive a few drops of oil. If you can’t decide which of your requirements takes priority (moisture vs scent), buy a model that lets you bundle oil and water in the same liquid reservoir.


After settling the above debate, make your final decision. If you end up on the less humid side of life, we recommend investing in the Honeywell HCM 350W. But if your domestic needs are decidedly more diffuse, opt for Essential Wellness’ diffuser.

My name is Bob Wells and I am a retired HVAC tech from Washington state. I am currently retired and no longer do much with HVAC, however, I feel like I have a lot of knowledge in the subject and I wanted to create a website where I could talk about what I've learned and help upcoming HVAC techs. Find more info about me and HVAC Training 101.