Fogger Droplet Size and Effectivity, Compared

The droplet size produced by different fogging devices and insect repellents differs a lot. The size of these particles plays an important role in determining what type of insects they’ll affect.

Since different types of sprays work better in different types of applications, each produces droplets of a certain size. In this article, we’ll compare the droplet size from aerosol sprays, thermal foggers, and ULV foggers. We’ve also gathered information on the most effective droplet size to combat different types of insects and pests.

spray, thermal and ULV fogger droplet size

Droplet Size Overview

The droplet size that is most efficient for each type of insect will depend on that insect. For example, for smaller insects like mosquitoes, smaller droplets are going to work better. For larger insects like flies, larger droplets will be more effective.

The area you’re going to use the spray or fogger is also important. In indoor areas, you can use smaller droplets since there is no wind. This means that the droplets will be able to settle on all areas that need treatment, including hard-to-reach places. This is more difficult outdoors since sprayed droplets are subject to weather conditions like wind and rain.

If you want to use droplets that are smaller than 5 microns, the slightest breeze is going to blow those droplets away from the target area. This makes it much more difficult to fog an outdoor area efficiently with smaller droplets. It’s more common to use larger droplets outdoors. They’re heavier, so a small breeze won’t blow the fog far from the area that you want to treat.

Average droplet size in microns

One micron is 0.001 mm or 0.00004 in.

The droplets produced by thermal foggers can be as small as 5 microns. The droplets from ULV foggers can vary from 10–30 microns in size. Aerosol sprays generally range from 30–50 microns.

For visualization purposes, let’s compare those to human hair. One strand of human hair is about 70 microns thick, on average, so the droplets produced by a thermal fogger are almost 150 times smaller than a human hair.

Droplet Sizes by Fogging Method

Aerosol Sprays

insect repellent spray

Aerosol sprays are the most common insect repellents for personal and home use. These cost much less than foggers but are much less efficient and can’t be refilled. You can only use them until they run out of liquid.

Most aerosol sprays contain insect-repelling substances such as DEET. The droplets produced by aerosol sprays can vary in size but are usually within the 10- to 50-micron range, while the majority will be in the 30- to 45-micron range.

Aerosol sprays will be effective if you can spray them close to the area you want to treat. Most aerosol sprays can only spray short distances, which isn’t going to be effective for fogging an entire outdoor area. Droplets that are larger than 30 microns, like those produced by aerosol sprays, will be less effective against mosquitoes than smaller droplets. They’ll also be unable to get into the small, hard-to-reach areas to eliminate as many mosquitoes as possible.

This is why aerosol sprays generally repel mosquitoes and other pests without killing them. These larger droplets are good for spraying directly on the skin or clothing, making aerosols perfect temporary insect repellents. They generally don’t contain an insecticide, but some sort of insect repellent liquid instead.

Thermal Foggers

Bonide Mosq Out Insect Fogger

Thermal foggers are the most efficient type of foggers since they can produce the smallest droplets of all the different types of foggers and sprays. These foggers use heat to vaporize the insecticide and turn it into a dense fog with droplets that are approximately 5–10 microns in size.

The size of the droplets produced by a thermal fogger can differ based on a few factors. These include the type of insecticide, the temperature of the burner and coil, and the fogger’s flow rate.

Since thermal foggers are able to produce such small droplets, there are important rules to follow for successful fogging. For example, the best weather conditions for fogging will be windless or nearly windless. Even a small breeze will be able to blow these tiny droplets away from the area you wanted to treat.

Also, you’ll need to fog close to the area where the mosquitoes live. Fogging from a distance isn’t going to be effective as these light droplets can fly in any direction if you fog from a distance. For safety, the person operating the fogger must stand upwind to ensure that the fog isn’t blown back at them.

ULV Foggers

Longray Carryall ULV Fogger

Ultra-low volume (ULV) foggers use air pressure and a special nozzle to break a liquid into droplets, which are then sprayed out as fog.

They can’t produce the same size droplets as thermal foggers but are very efficient in comparison with aerosol sprays. ULV foggers can produce droplets that are approximately 5–30 microns in size.

Unlike thermal foggers, you can easily adjust the droplet size produced by ULV foggers. This means that you can change the droplet size for different insect treatments as well as for different areas.

These cold foggers are used more often in indoor areas than thermal foggers. Their advantage here is that they don’t get hot (or use fire as thermal foggers do) and produce a practically invisible fog. Because ULV foggers need electricity to work, however, they aren’t as handy for outdoor use as some thermal foggers, which use propane or butane gas, have a portable design, and can be carried around easily while fogging.

Recommended Droplet Sizes for Different Pests

Agricultural Pests

agricultural pests


The fogging droplets produced for agricultural pest control are generally larger than those used for insect elimination. This is because agricultural foggers are usually installed in some sort of vehicle and sprayed out in large quantities.

The pests found in agricultural applications are larger, so the fogger can use larger droplets and still be effective. The average droplet size for agricultural applications can vary significantly based on the area you want to treat and the target insects. So, the recommended droplet size here can vary from 70–200 (or even 300) microns in size.

Larger Insects and Flies


To terminate larger insects such as flies, wasps, and so on, you’ll want to use a fogger that produces droplets that are approximately 30 microns in size. Most ULV foggers can produce droplets of this size as can some thermal foggers and some sprays made specifically for these types of insects.



Mosquitoes need to be controlled to avoid the spread of mosquito-borne diseases such as malaria, yellow fever, and so on. Mosquito foggers are used to control mosquito populations in many different areas. Since mosquitoes are pretty small insects, you should use tiny droplets. The most effective droplet size to control a mosquito problem is from 5–25 microns. This droplet size will work on the majority of mosquito species.

It’s important to produce droplets in the 5- to 25-micron range. Going above or below that range can really decrease the efficiency of your fogging. Droplets larger than 25–30 microns are heavier and will fall to the ground faster. If they only stay in the air for a short amount of time, they won’t be able to reach the majority of the mosquitoes.

If the droplets are smaller than 5 microns, the slightest wind will blow them away – before they can even reach the area you wanted to treat. Extremely tiny droplets may not be effective on all mosquito breeds, either.

Both thermal and ULV foggers are effective at eliminating mosquitoes in indoor and outdoor areas. For indoor areas, ULV foggers will be more successful. For outdoor areas, a thermal fogger is the most effective tool for mosquito control. Both of these fogger types can produce droplets in the 5- to 25-micron range.


If done correctly, fogging is an excellent way to achieve pest control. When done regularly, it can even achieve longterm results.

The type of pests you’re going up against, the area to be treated, the weather, and the fogger you’re using all influence the droplet size. To choose the best option for you, you’ll have to consider all of these factors.


Maxcy Nolan

How can i test the particle size of my fogging equipment?


    Hi Maxcy,
    It would be difficult to test the particle size of the fogging equipment at home, as the particles produced by these devices are usually measured in microns, which means that they are thinner than a human hair. Your best chance is to look at the user’s manual of the fogging device you have purchased or contact the manufacturer of the device and they will provide you with the correct information about the particle size the device will produce.

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