Does it matter if a humidifier is warm or cold air mist?

By Eric Hopper | Last updated: December 17, 2021


Both warm-mist and cold-mist humidifiers can be used in an indoor garden to increase humidity levels. However, they operate in very different ways. Because of their differences, a grower may find that either the warm mist or cold mist is better suited for his or her indoor garden. A look at the advantages and disadvantages of each type of humidifier will help a grower decide which is best for their indoor garden.

Warm-mist Humidifiers

Warm-mist humidifiers are designed to create a warm mist from heated water. In fact, most warm-mist humidifiers heat up the water to its boiling point, which greatly reduces the likelihood of molds and bacteria. Warm-mist humidifiers will increase the ambient air temperature within the growroom. This can be an advantage or a disadvantage depending on a growroom’s current heating/cooling requirements. For most indoor gardens, additional heat is unwanted because of the excess heat given off by horticultural lighting equipment. That being said, many growers prefer to use a warm-mist humidifier during the winter months when the ambient air temperature is naturally cooler.

Cool-mist Humidifiers

Cool-mist humidifiers disperse a cool spray/mist into the air. The mist is released at room temperature and is not actively chilled. The two types of humidifiers that fall into the cool-mist category are evaporative humidifiers and ultrasonic humidifiers. Because they do not heat or chill the water, cool-mist humidifiers generally require less electricity to operate than warm-mist humidifiers. The lack of heating/cooling elements also makes cool-mist humidifiers the less expensive option. Cool mist humidifiers are available in many shapes and sizes, so there is an option for just about any size indoor garden. Cool-mist humidifiers will not raise the temperature of the air in the grow space. This is advantageous for any indoor horticulturist battling excess heat. The biggest disadvantage of cold-mist humidifiers is they need to be cleaned and sterilized regularly to minimize the chance of molds or bacteria establishing within the water-holding chamber or within the humidifier’s internal components.

Maintaining optimal humidity levels within a growroom can be difficult and the use of a humidifier, in many cases, is a grower’s best option. A cool-mist humidifier is probably the best option for growers who are already combatting excess heat from lighting equipment. Indoor gardens that can handle, or even require, the additional heat produced by a warm-air humidifier can humidify the air with less worry of molds or bacteria forming in the humidification unit. Regardless of which humidifier is the better fit, maintaining humidity levels conducive for accelerated growth will reward an indoor gardener come harvest time.

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Written by Eric Hopper | Writer, Consultant, Product Tester

Profile Picture of Eric Hopper

Eric Hopper’s past experiences within the indoor gardening industry include being a hydroponic retail store manager and owner. Currently, he works as a writer, consultant and product tester for various indoor horticulture companies. His inquisitive nature keeps him busy seeking new technologies and methods that could help maximize a garden’s performance.

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