What Are Cold Foggers and How Do They Work?

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What are cold foggers?

A cold fogger is a device you can use to fight pest problems both indoors and outdoors. You can also use them to disinfect indoor spaces, as well as get rid of mold and unpleasant odors.

A cold fogger is “cold” because it’s the opposite of a thermal fogger. Cold foggers don’t use heat to vaporize the fogging liquid and turn it into a mist. Instead, they use cold spraying methods, which, in most cases, use high air pressure to spray the fogging liquid out in tiny particles.

Cold foggers usually come either in a handheld fogger or a backpack fogger. The handheld versions are usually cheaper while the backpack cold foggers are easier to carry and therefore more practical.

The most popular type of cold fogger is the ultra-low volume (ULV) fogger. Most of the time, ULV foggers are considered the same as cold foggers.

How do they work?

Inside the casing of a cold fogger is an electric motor. This is the main part of a ULV fogger since it is responsible for turning the liquid into tiny droplets. The power of the airflow will depend on the power of the motor.

The motors of most handheld foggers are approximately 1-3 horsepower (HP) but vehicle-mounted foggers have much more powerful motors, up to 20 HP. Some cold foggers use oil-based fogging solutions while others use water-based solutions. There are foggers that can be used with both types of solutions. The fogging solution goes in the tank which is either in the body of the fogger or attached to the bottom of the machine.

Most cold foggers work using electricity. This means that you must have a power outlet near the area to be fogged or an extension cord that can reach the target area. Some, however, are battery-powered and others use gasoline to power the motor.

When you turn the fogger on, the motor will pump the fogging solution out of the tank. A blower then sprays the liquid out through a special nozzle located on the front of the fogger. This nozzle pressurizes the air (either by being small enough to confer high pressure or by having a vortex of high-speed air that the liquid is pumped through), turning the fogging solution into a fine mist.

Particle size

The advantage that ULV foggers have over thermal foggers is that they allow you to control the particle size. On standard ULV foggers, you’ll have the option of setting the particle size from 5–50 microns. You can adjust the droplet size a ULV fogger produces by changing the flow rate of the solution.

This is definitely useful if you need to fog in different areas.

You might want to use smaller particles indoors since they stay in the air longer and can reach smaller gaps and holes in the walls and floor as well as the spaces behind furniture and other tight spaces. Smaller particles are better when you want to kill mosquitoes since the most effective droplet size for this is from 10-15 microns.

For larger insects that live outdoors, you’ll want to use a droplet size at the higher end of the spectrum. Even a small breeze can blow smaller droplets away from the target area. Larger particles, on the other hand, will reach the target area even in slightly windy conditions.

Cold fogger use

Cold foggers are often set in automatic mode and left to fog an indoor area since there’s no need to have a person operating the fogger (unless they are gasoline-powered). Gasoline-powered cold foggers and thermal foggers should not be run unsupervised due to the fire risk.

It wouldn’t be effective to leave a fogger in a static place for a long time when fogging outdoors, though. Some ULV foggers come with a special flexible hose and a handle to allow you to use them as portable foggers, walking around and fogging hard to reach areas.

Fogging with a cold ULV fogger

Fogging with a cold fogger

Cold fogger prices

When looking at cold fogger prices, the average price starts around $200. This can rise to $1000+, depending on the power, capacity, and functionality of the fogger.

In comparison, you can get a basic thermal fogger for just $50. Keep in mind that a professional thermal fogger can cost $1000+, too.


Elisabeth Lino

Can you used nadcc tablet disinfectant with this machine?
Do you also sell hot fogging?


    These tablets should be fine for use with cold foggers.
    As for selling, no, we do not sell anything, we make reviews on products. If you’re interested in foggers, you should read this article.

Nichelle powers

Will this fog affect electronics?


    Since the foggers do create a mist, we suggest removing or at least covering the electronics (if the removal isn’t possible). Often the electronics will be fine after the fogging, yet, there is no guarantee so we suggest not taking that risk.

Peter Fraser

Hi My ULV Cold fogger after a few mins the outside of the motor gets very hot this spreads to the head of my machine is this normal I fear the plastic may melt


    You should check your manual, perhaps it mentions something about this happening. If not, try contacting the manufacturer or the seller of the product. This shouldn’t be happening, we suggest not using the fogger until finding out what seems to be the problem.

Kay Williams

How does the fogging affect oil paintings?


    We haven’t had experience with oil painting, though, we would suggest removing the paintings before fogging. If that’s not possible, try to avoid getting the fog on your artworks as much as possible. Make sure the paintings are completely dry before touching them. We also do not suggest fogging the paintings themselves.

Shideh Moddjarrad

How often fogging needs to be done if it is for purpose of disinfecting the area?


    We’re not experts in cleaning and disinfecting, however, it depends on the use of the space you want to keep clean and the level of exposure it has had to viruses and bacteria.


Hi, I am very chemically sensitive, so I’m looking for a way to pump fog to fill the underneath of my house (low clearance) with the addition of clove oil to kill mould.
Can you recommend a hot or cold fogger for that purpose?
Also, what is in fogging solution?
Can I get a plain one to add my own active ingredient to?
Cheers, Megan.


    There are different fogging solutions, including different ingredients. If you have sensitivities, you should probably look into more natural solutions. As for what kind you can use depends on the fogger you choose. Some will work with both water-based and oil-based solutions, while some will only work with either one of those. As for whether to choose a cold or hot fogger, that’s up to you, but we do suggest keeping in mind that thermal foggers pose certain fire hazards.

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