10 Best Humidifier for Grow Tent & Grow Room (Review 2020)


Honeywell Germ Free Cool Mist Humidifier

Venta 2-in-1 Humidifier and Air Purifier

Pure Ultrasonic Cool Mist Humidifier

If you’re a seasoned indoor gardener, you don’t need to be lectured about the importance of investing in the best humidifier for grow tent.

Novice indoor gardeners may not know that regulating the humidity level in a grow room is a major challenge. The reason’s that the moisture in the air tends to fluctuate every often, and indoor plants needs a certain level of humidity for vibrant growth.

Fortunately, humidifiers have been fine-tuned to play the role of Mother Nature perfectly. A good humidifier for grow tent offers a convenient and a relatively inexpensive way of controlling the humidity level in every growth stage.

Even so, humidifiers come in a plethora of styles, and choosing a perfect option for your grow room may take a bit of learning curve.

No need to worry though, because we’ve evaluated different humidifiers based on multiple factors: capacity, runtime, energy consumption, longevity, and so much more.

Throughout our hands-on testing, the Honeywell HCM350W Cool Mist Humidifier stood out from the batch. It’s the best grow room humidifier that provides the best bang for your buck

Now, spare a few minutes of your precious time and check out other humidifiers for indoor growing that met our robust testing criteria this year.  

10 Best Humidifier for Grow Tent


Product Name

Key Features


Best Overall

Honeywell Cool Mist Humidifier

Premium Pick

Venta 2-in-1 Premium Humidifier

Great Value

Pure Enrichment Cool Mist Humidifier

Vornado Evaporative Humidifier

AIRCARE Evaporative Humidifier

URPOWER Ultrasonic Humidifier

LEVOIT Cool Mist Humidifier

Crane Drop Cool Mist Humidifier

Pure Guardian Ultrasonic Humidifier

TaoTronics Cool Mist Humidifier

Key features

Need the best germ-free humidifier for your medium-large grow room? The HCM350W Honeywell Germ Free Cool Mist Humidifier will do the trick. It covers up to 500 square feet of your grow space to keep your indoor environment fresh and promote healthy plant growth.

It delivers pure, germ-free air using the state-of-the-art UV technology, which kills 99.99% of germs in water. It banishes all microbes including bacteria, virus, mold, and fungus. What’s more, the HCM350W runs for 24 hours on low speed, with 3-speed settings for adjusting moisture output to your liking.   

What I Liked

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Key features

One of the biggest advantages of the Venta LW15 is its 2-in-1 capability. This premium choice humidifier is capable of humidifying dry room air while at the same time removing dust, pet dander, dust mites, and other allergens down to 0.3 microns. Thus, it completely humidifies your grow room while simultaneously purifying it, allowing your plants to enjoy odor-free and fresh air.  

The LW15 serves as both a filter-free air purifier and filter-free evaporative humidifier. It uses Cold Evaporative technology, which means it doesn’t produce white dust like traditional humidifiers. It’s indisputably one of the best grow room humidifiers on the market today.

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Key features

This is our runners-up option that befits small grow tents of up to 250 square feet of area size. What makes the Pure Enrichment MistAire Ultrasonic Mist Humidifier the best humidifier for small grow tent is its low electricity consumption. This super savior of electricity boasts a 120V and 50Hz power rating, yet turns water into mist without fuss.

The small grow tent humidifier comes equipped with a 360-degree mist nozzle, which helps you direct the flow of mist to areas of your grow tent where there are no lights or other electrical equipment. It also features an automatic shutoff, whose role is to turn the unit off when the water level is low or when the water tank is detached.

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Engineered and built by Vornado, the EV100 whole room humidifier covers up to 300 square feet of space using natural evaporation. It keeps your large grow room environment fresh by expelling dust and white dust to ensure healthy plant growth.

Its 1-gallon water reservoir offers up to1-gallon output in every 24 hours. It also brings the 3 fan settings on board for a personalized humidity control experience. Besides the simple controls, the EV100 has 6 output levels ranging from 40% to 60%. It guarantees optimal humidification for most grow room plants.

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The AIRCARE is one of the biggest humidifiers intended for maximum reach up to 2700 square feet. It uses a gigantic six-gallon water reservoir to humidify your 5×5 grow tent continuously for up to 70 hours – without refilling.

This big humidifier for large grow tent features an intuitive digital control panel with three fan speed settings: nighttime, medium, and high speeds. The panel also houses a droplet icon, which enables you to adjust humidity from 5% to 65% for maximum elimination of virus particles from the air.

What’s more, the unit includes an auto humidistat that tells you when it’s time to replenish the tank or check the filter.

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The URPOWER MH501 is the best commercial grade humidifier for indoor growers whose location has a winter. This cool mist unit generates vapor using the Ultrasonic technology and adds moisture back into the air. Thanks to its 5L reservoir, it achieves a max mist volume of 300ml per hour for a whole night of humidification.

We loved its uncomplicated operation with a one power button control. You’ll be able to choose from low-medium-high humidity levels depending on your desired grow room humidity level. It also allows you to adjust from 45% to 60% humidity levels to attain the ideal environmental humidity for your plants.

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Key features

With a 4-liter water tank capacity, the LEVOIT Ultrasonic is undoubtedly the best humidifier for a 4×4 grow tent. This BPA-free, ETL listed and CA65 tested cool mist humidifier offers you a 40-hour runtime on low setting, and a 10-hour continuous operation on high setting. Its runtime can be shorter or longer depending on your grow tent’s environmental temperature and humidity.

When it comes to the ease of use, this humidifier for 4×4 grow tent has an easy-refill tank with a 3.8inch/9.65cm opening. You’ll find it convenient to refill the tank or clean up the interior of the humidifier. It’s equally reliable in terms of safety, because it features an automatic shut-off function, which switches off the unit when the tank runs empty or when you lift up the water tank.

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Key features

Looking for the best affordable humidifier for your grow room? This Crane Drop Ultrasonic Humidifier is your ideal option. It features a 1-gallon detachable tank and an adjustable 360-degree mist lid, which can humidify a large grow room up to 500 square feet. It’s the best for large grow rooms.

The 360-degree lid helps target mist to your required direction. And you can change speeds using the variable output speed settings that come with the unit. More importantly, this humidifier integrates a clean control anti-microbial material, which kills up to 99.96% of molds and bacteria in water.

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Key features

The Pure Guardian H965AR has all the features you’d need to create the perfect humidity conditions for your cannabis plants in a medium size grow room. Using a one-gallon water reservoir, the H965AR can operate from 15 hours through to 70 hours depending on your settings. It can also humidify up to 320 square feet of space.

Unlike traditional humidifiers, this one doesn’t grow slimy mold on the surface of the water tank. It uses a Silver Clean Protection technology to fight against the growth of greasy mold and mildew. This guarantees clean water all the time.

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Another best humidifier for 2×4 grow tent is the TaoTronics Ultrasonic Humidifier, whose coverage is anywhere between 107 and 322 square feet. It gets the backing of a 4L tank capacity, with a full tank lasting for 12-30 hours. The misting duration relies on the settings you apply.

What sets this cool mist humidifier apart from the other options is its informative LED display built into it. It shows you the RH levels in real time, which are recorded by a built-in humidistat. You’ll be able to choose between three misting levels, whereby the humidity level of 40-60% is recommendable.

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Most Important Information About Grow Tent Humidifiers

What is a humidifier and how does it work?

Simply put, a humidifier is an electrical appliance that emits vapor or steam to increase the humidity or moisture in a compacted space, such as a grown room. It’s also used in several other settings, including greenhouses, offices, restaurants and many other areas where the humidity of the air has to be controlled.  

A good humidifier for grow tent proves useful in lowering the rate of evapotranspiration for better growth of plants in your indoor grow tent.

 Plant humidifiers are different in functionality. Some tend to add warm moisture to a grow room, while others add cold moisture. Supplying your plants with wrong humidity levels can negatively affect their growth.

Too much moisture in a grow room encourages the growth of microbes like mold and bacteria.  These microorganisms not only lead to death of plants and failure of crops, but also cause other conditions like crown rot.

Furthermore, excessive humidity in the atmosphere attracts pests like fungus gnats, whose larva often thrives in moist soil and feed on plant roots.

Scientific studies have also shown that a steadily declining relative humidity is detrimental to the growth of your plants in a controlled environment, such as a grow room.

Low humidity environments affect how plants remove carbon from the atmosphere. These conditions create a demand that draws water from plants.

Plants tend to shut their stomates (small pores on their leaves) during dry weather to avoid losing excess moisture. When this happens, plants won’t be able to capture as much carbon since the stomates are responsible for CO2 uptake.

 Now you might be asking yourself: How does a humidifier work?

You’ve just learned that a humidifier induces moisture in the air, but how the heck does it work?

To understand how this stuff works, we’ll need to take a tour into the inside of one common type of humidifier— an evaporative humidifier.

This is the most basic type of humidifier which, for the most part, is self-regulating. An evaporative humidifier consists of a reservoir for holding cold water and for dispensing it into a basin.

It also has a moisture-retentive wicking filter for absorbing water from the basin. Then there’s a fan whose role is to blow air through the moistened filter.

The air evaporates some of the water as it passes through the filter, while the fan blows out moisture into the room. It’s harder to evaporate water from the filter when the relative humidity is higher. This is because most evaporative humidifiers have a self-regulating feature.

Excessive humidity in the air naturally decreases the humidifier’s water-vapor output. Evaporative humidifiers are effective in preventing dust from being created in your indoor grow room.

It’s easy to track your grow room’s humidity level using an inexpensive hygrometer. This device displays the exact relative humidity in your grow room.

Types of plant humidifiers

There are four main types of plant humidifiers with distinctive characteristics. Each type of plant humidifier uses a diverse technology to introduce moisture into your grow room, and ultimately raise the level of humidity.

Without further ado, let’s discuss the different types of humidifiers for plants on the market.

Warm Mist Humidifier

This is among the most common types of plant humidifiers on the market today. Its functionality is never complicated.

A warm mist humidifier heats water up to a high temperature and converts it into vapor. The water-vapor is then released into the air as warm mist, thus boosting the humidity level of the surrounding environment.

Cool Mist Humidifier

This is another type of plant humidifier that’s commonly used in grow rooms. It comes with filters for removing impurities from the water.

It then ejects germ-free cool mist into the atmosphere. A cool mist humidifier operates for a longer time and uses less electricity than its warm mist counterpart.

Evaporative Humidifier

An evaporative humidifier is also often used to bath plants with moisture in grow rooms. It uses airflow to generate vapor, and shares the same working principle with swamp coolers.

This humidifier draws water from its tank over a wicking material (such as felt or cloth). It contains a fan that forces air over a damp wicking material and turns it into mist. The vapor or mist is then blown into the dry air, raising the humidity level for your indoor growing plants.

Ultrasonic Humidifier

This is a unique type of plant humidifier, which utilizes ultrasonic vibrations to steam the water in the tank. Its vibrations increase the evaporation rate of water, thus converting it into extra-fine droplets.

These fine water droplets are then dispersed into the air. It’s easy to differentiate an ultrasonic humidifier from other plant humidifiers. This one creates the finest mist, and has no filters. Also, it’s quieter and more expensive than other humidifiers.

Reason to use a humidifier in grow Tent

Using the best grow room humidifier is a recommendable approach to keep their surroundings moist and enhance their healthy growth. To better understand the reason to use a humidifier in a grow room, let’s stop a little and think about how plants absorb air from their surroundings. 

Fact is, all plants respire carbon dioxide (CO2) from their surroundings through their leaves. And when this happens, it’s natural for them to lose some of the water conserved in their foliage.

Dry air accelerates the loss of water by plants when respiring. As the atmosphere becomes excessively dry, plants lose more water than they can recoup via their roots.

With too much loss of moisture, plants react by almost entirely closing their pores to minimize further moisture loss. Of course, closing the pores helps reduce moisture loss. But then again, it means that plants won’t receive the much-needed CO2 from the environment.

Ultimately, the cells of your indoor plants will die, and their leaves will become limp and ill. By using a grow room humidifier, your plants’ leaves will be more vibrant.

And vibrant leaves can greatly help plants grow healthily, since leaves are responsible for manufacturing food for the whole plant. Adequate moisture is key to the manufacture of food.

As if not enough, grow room humidifiers reduce infections from the common culprits of diseases, such as bacteria and viruses. Mind you, these agents of plant diseases never survive in humid conditions.

Furthermore, if your plant is scarred or has a fungal infection, a sufficiently humid grow room can speed up its recovery.

Humidifiers help leaves heal up quite fast, and make the plants lively. The right level of humidity also contributes to getting rid of dullness, dryness, and tipping of leaves.

Besides, plants thrive in warmer conditions. And humid air is warmer than dry air. Turning on the humidifier in a grow tent increases the grow room warmth.

Consequently, you won’t need to use a heater to warm your indoor plants. This helps you save a few bucks for other purposes. Awesome, huh!

Anyways, low humidity leads to discoloring of flower buds, and eventually falling off the plant. With dry air, flower buds turn brown, which means the reproduction of plants won’t be possible. And yet, the reproduction is essential for species survival and propagation.

By simply raising the humidity to sufficient level in your grow tent, the buds will bloom into flowers leading to species reproduction.  

What is the optimum level of humidity for plants in grow rooms?

To better understand the optimum humidity level for plants in your grow room, you need to know what “relative humidity” is. Humidity itself is the amount of water vapor in the atmosphere.

However, you need to know that the amount of moisture the air can hold at a given time depends on the temperature at that specific time. Naturally, hot air holds more vapor than cold air.

Relative humidity refers to the amount of moisture air can hold at a specified temperature. A relative humidity of over 100% means air can no longer hold the excess water. And the surplus is condensed into fog, morning dew, or rain.

For instance, imagine your grow room temperature is 30˚C (86˚F) with a 33% relative humidity (RH). Now, you’re aiming to rapidly cool down your grow room environment to 10˚C (51˚F).

In this scenario, the RH is going to rise to 100%, which is called the Dew Point. If you were to decrease the temperature further, the moisture in your grow environment would start to condense.

Now let’s tackle the elephant in the room: what is the optimum level of humidity for plants in grow room?

Well, the ideal humidity level for your indoor cannabis would vary based on the stage of your grow, geographic location, strain, and season. Plants native to tropical areas tend to better adapt to hotter temperatures.

Plants native to tropical climates are gonna grow best at higher RH levels than those native to colder, more temperate climates.  Again, cannabis plants have different requirements at each growing cycle.

Below is a chart representing the optimum humidity level at each of the four growth stages:

  1. Cloning Stage: 75% – 85%
  2. Vegetative Stage: 50-70%
  3. Flowering Stage: 50-60%
  4. End of Flowering Stage: 40/45%

Note: Excessive humidity causes slow growth, bud rot and mold on leafy plants or fat buds. Declining humidity leads to retarded growth and leaf stress. 

Cloning Stage: Optimal grow room humidity 75-85%

Cloning occurs when clones are separated from their mother plants and lasts around a week. Since young clones are yet to develop roots, they solely depend on their leaves for water. They take time to form a root system for water intake, and thrive in high humidity of 75-85%.

You need to maintain high humidity levels and around 75-80˚F optimum temperature for the clones to increase their growth and create a rooting system. After they’ve formed their roots, you can lower the humidity to 60-65%.

Veg/Vegetation Stage: Optimal grow room humidity 50-70%

Seedlings and young cannabis plants take about a month in the vegetative stage. In this stage, plants are gaining leaf mass and developing their structure and immune system. It’s easy to differentiate between male and female plants during this stage.

You gotta maintain an optimal grow room humidity of 50-70%  and temperature of 70-80˚F at this stage, because plants have developed a strong root system to aid in water and nutrient transfer.  A higher humidity allows plants to grow at a faster pace, while a lower humidity encourages slow growth during this stage.

Flowering Stage: Optimal grow room humidity 50-60%

Essentially, you need to lower the relative humidity of your grow room to 50-60% at the onset of the flowering stage. Flowering is the last growth stage when plants are approaching harvest.

This growth cycle takes between 8 and 12 weeks. And the optimum grow room temperature has to be around 65-70˚F during the day, and 45-55˚F at night.

At this point, most indoor growers use vapor pressure deficit (VPD) recommendations to give their plants much needed comfort. A 60% or lower optimum humidity level facilitates the bud production. If you’re growing cannabis, a lower humidity at this stage allows your plants to produce more resin.

End of Flowering: Optimal grow room humidity 40-45%

During this stage, plants have already grown large and dense. They’re taking in a lot of water as they’re approaching harvest. You’re better off adopting the defensive at this stage by lowering the grow room humidity to 40-45%.

 Also adjust your optimum temperature to around 65-75˚F. The end of flowering stage is when the value of your cannabis plant is at its prime.

Frequently Asked Questions (FAQs)

The following are some of the common questions our audiences are asking concerning humidifiers for grow rooms.

Should I put a humidifier in my grow tent?

Yes, you gotta put a humidifier in your grow room besides providing grow room ventilation and lighting. Plants in your grow room will require different levels of humidity in the air at different growth stages, such as cloning, vegetative, and flowering.

For example, plants would need an optimal grow room humidity of 75-85% during the cloning stage to help them develop advanced rooting system. Then, throughout the vegetative stage, you have to maintain an optimal grow room humidity of 50-70%.

At this stage, your plants have developed a strong rooting system, and would require a higher humidity to grow faster.

Is cool mist or warm mist better for plants?

Good question. The thing is, it’s fine to use either a cool-mist humidifier or a warm-mist humidifier depending on your grow room’s temperature. A cool-mist humidifier is the right option to use if it’s getting too warm in your grow room.

A warm-mist humidifier heats water up to a boiling point and would create a warm area. For a better understanding, let’s discuss the two options side by side.

Warm-mist Humidifier: This option uses heated water to create a warm mist. It increases the ambient air temperature in your grow room, which significantly reduces the growth of molds and bacteria. We’d suggest using a warm-mist humidifier throughout the winter period when the ambient air temperature is cooler.

Cool-mist Humidifier: This option disperses a cool mist/spray into your indoor grow room. It dispenses the mist at room temperature, and is not actively chilled. A cool-mist humidifier won’t raise the temperature in your tent grow, and is a perfect option if you’re already battling excess heat from lighting equipment.

What happens if humidity is too low in grow room?

Too low humidity in your grow room isn’t good for your plants as it causes stagnated growth or even death in severe cases. When the humidity level is too low, your indoor plants will become dehydrated, resulting in closing of the stomata.

Stomatal closing causes slow photosynthetic process due to carbon limitations. This leads to stress, retarded growth and compromised yields.

Severely low humidity conditions will cause the plant to wilt and die. With complete lack of atmospheric water, grow room plants won’t be able to uphold their protective mechanisms due to the stress imposed by water loss.

What would happen if there is excess humidity in my grow room?

Excess humidity in your grow room is good for your plants right? Wrong!

Too much moisture buildup in your grow room results in rotting, such as flower or bud rot. It may also result in white mold collecting on your leaves and hindering your plants from taking in water and light. Again, white molds feed on your plants rendering your yield useless.

Excessive humidity may also cause slowed transpiration, because it reduces the rate at which plants draw water from the soil. The excess water creates the smaller-than-normal water gradient between the atmosphere and plants.

This anomalous water gradient causes diminished nutrient uptake efficiency, ultimately leading to nutrient deficiencies. This phenomenon commonly affects calcium uptake.

Furthermore, saturated media PH tends to rise over time leading to complete unavailability of nutrients like metals and phosphorous.  Chemical interactions are altered under elevated PH conditions.  

What is the optimum humidity level for plants?

The optimum humidity level for indoor/greenhouse cultivation will vary based on the stage of growth and plant species. Most plant species require between 50% and 60% optimum humidity level.

Below is the recommended optimum humidity level for cannabis plants according to their stage of growth: 

  • Cloning: 75-85%
  • Vegetation: 50-70%  
  • Flowering: 50-60%
  • End of Flowering: 40-45%

What kind of water should I use in my humidifier?

You should use distilled water, demineralized water or purified water in your humidifier as it contains less mineral buildup. Using tap water or unfiltered water is not advisable because it contains mineral deposits that promote the growth of microbes like bacteria, mold and viruses.

What is the best humidifier for grow tent?

There’s no one-size-fits-all when it comes to humidifiers for grow tents. However, there are certain features to consider while choosing the best grow room humidifier. Watch out for the following essential pointers:

Area Coverage

You need to figure out the size of your grow room before settling on your best grow tent humidifier. By measuring your grow space, you’ll be able to determine the right model that’ll adequately cover your room. Models that can cover up to 600 square feet of the area are ideal for larger grow rooms or tents.

Water Tank Size

A water tank is an integral component of the working mechanism of every humidifier out there. The size of tank varies from model to model. Units with smaller one-gallon tank need to be refilled every 12-16 hours, while others with bigger six-liter tanks have less water changing frequencies.


Humidifiers do not run forever. These appliances operate according to their runtime. Some humidifiers last more than 60 hours, while others can only manage around 15 hours. You have to consider the runtime since replenishing the water level every often is strenuous. For instance, humidifiers than run for 15 hours would need to be refilled twice in 24 hours.


The best grow tent humidifier shouldn’t be rocket science to operate. For maximum user-friendliness, choose a model that’s easy to assemble, maintain or transport from place to place. If possible, go for units with fewer buttons and more intuitive LED display indicating humidity level and fan speed.

Humidistat (Safety Feature)

A humidistat is more or less the same as a thermostat. It automatically shuts off the humidifier once the desired moisture level is reached or when the tank needs to be refilled. This feature helps prevent over-humidifying your grow room or operating your appliance on an empty tank.


A timer works hand in hand with a humidistat to prevent your grow room from over-humidification. Having a timer is a life saver. You’ll be able to set the unit to stop humidifying the room at your specified time.


A good humidifier for grow tent should have a portable style and design. If you prefer a large humidifier, then opt for one with wheels for easy transition from one room to another. Also, humidifiers need constant refilling, so make sure the water container is portable and easily refillable.

Humidity Settings

Also known as the misting settings, the humidity settings refer to the amount of humidification the device can perform. Some options have high settings and can mist 300ml of water per hour, allowing for faster humidification. Even so, choose smaller settings for smaller grow rooms. And make sure the unit has at least three humidification settings.

Ease of Cleaning & Maintenance

The best humidifier for grow room has to be easy to clean and maintain. A clean unit dispenses cleaner and safer moisture for plants. Ensure that the humidifier of your choice can be maintained through a DIY approach – without having to incur additional maintenance costs.  

Final Thought & Expert Endorsement


Now you’ve gotten the complete list of the 10 best humidifiers for grow tents and grow rooms. We recommend picking a humidifier based on your specific needs and preferences.

And, remember, your grow room should just be humid and not too wet to ensure a perfect atmosphere for your plants to thrive.

The Honeywell HCM350W Cool Mist Humidifier is inexpensive, simple to operate, and reliably spreads mist in your grow room without much fuss.

Anyways, we sincerely hope this comprehensive review and guide on the best grow room humidifiers will help you make an educated purchase decision.

Best of luck!