What is a Mosquito Fogger?

By: Peter
Last updated:
man using a thermal mosquito fogger

There are several ways of eliminating or repelling mosquitoes, but it’s hard to be completely protected all of the time unless you are completely covered up or you put a mosquito repellent on your bare skin.

A mosquito fogger can help, it’s an additional tool in the fight against mosquitoes. This isn’t a permanent solution, but it can give you a few hours of protection against adult-biting mosquitoes, so it might be worth considering.

You can either do the fogging yourself or hire a professional service.

Mosquito Foggers

A mosquito fogger is a device, that disperses an insecticide or repellent solution with a tiny droplet size. In other words, a sprayer that produces a spray with very fine particles.

For most people, a handheld fogger will be sufficient, but there are backpack foggers for larger backyards, and local government agencies or mosquito control districts may use truck-mounted foggers to treat mosquito problems.

You can spray the mist around your backyard to kill or repel mosquitoes. The skeeters prefer to avoid direct sunlight and look for shady areas to hide during the day. The fine fog will penetrate foliage and hang in the air longer than regular sprays.

What Do Foggers Do?

A mosquito or insect fogger sends tiny droplets of an insecticide into the air in the form of a fog. When a mosquito or other flying insects encounter one of these droplets in flight, they are killed.

A fogger is not employed to eliminate troublesome mosquitoes completely, but to give you immediate protection that most users say lasts about 6 hours. One of the useful things about a fogger is that you use it when you need to.

For example, perhaps you have friends coming around, and you want to eat outside, but you know you’ll be bothered by mosquitoes. A fogging treatment just before the meal should give you a bug-free moment. There are specific times you should use your fogger but more about that below.

When Should You Use a Mosquito Fogger?

The best time for fogging is the early morning or the evening. Mosquitoes are most active at these times. During the day, they avoid the sunlight and hide in the shade.

In the evening, the air temperature will normally be lower than the ground temperature, which means the fog will stay in the air longer and kill more insects.

For me, the most important reason is that most of the beneficial insects – bees, and butterflies – won’t be so active. The insecticide may kill other small insects besides mosquitoes, so it should be used with respect for other species.

This is what mosquito.org says about protecting pollinators;

mosquito management entities utilizing Ultra Low Volume (ULV) spray applications do so before dawn or after dusk to both target mosquitoes when they are most active and to avoid day-active pollinators such as butterflies and bees that have returned from foraging.

It’s also best to use a fogger when there is little wind. If there is a strong breeze, the fog won’t stay in the treated area for very long. Meaning fewer mosquitoes will be killed.

Wet or Dry Fog?

You may hear the term dry fog and wonder what that means.

A dry fog has a droplet size of 10 to 15 microns in diameter. The droplets are so small they seem to create a dry fog. When the droplet sizes are larger, 20 to 30 microns in diameter, this is a wet fog. It appears to be wet and is less dense than a fog.

Most ULV foggers can disperse dry or wet fogs, and thermal foggers give a dry fog with a droplet size of around 10 microns.

Dry fog is perfect when you need to disperse the fog over a wide area, as in mosquito control. A wet fog is great for applications such as disinfection, mold control, or targeting a precise area for pest control. A wet fog will leave surfaces wet and coated with the fogged solution.

The Different Types of Foggers

There are cold foggers (ULV ultra-low volume foggers), aerosol foggers, and thermal foggers (propane and electric).

A thermal fogger uses heat to produce a mist and a cold fogger uses pressure.

  • Aerosol Fogger

An aerosol fogger may be used like other aerosols you are probably familiar with. You push down the button or trigger and walk around your garden spraying. These are okay to use for small areas.

There are other aerosol foggers, total release foggers, also known as bug bombs, that can be used indoors. They are placed in the center of the room and are activated by pressing a button or removing a tab. They spray the contents of the can into the air in the form of a mist. You and your pets have to leave your home for several hours when using one of these foggers and air thoroughly when you return.

The bug bombs may be used to treat cockroaches, fleas, and silverfish with limited success as they don’t get the insecticide into the tiny crevasses where insects may hide. For just treating mosquitoes, they are not ideal.

Bug bombs may be flammable; always follow the instructions closely.

Cold Foggers

  • ULV Fogger

This is the most popular cold fogger; it can be a handheld or backpack. These foggers use high pressure to spray out the liquids. The pressure is created by a motor that can be powered by electricity, battery, or gasoline.

The fogging solution is stored in the tank. When the motor runs, the solution gets pumped out of the tank into a nozzle at high pressure. The fogging liquid is sprayed out of the nozzle in a fine mist. Some cold foggers use old-based solutions, others water-based solutions, and some both.

The particle sizes (from 10-50 microns) of a ULV fogger can be adjusted to allow the fogger to be used for different applications. Cold foggers can be used indoors and outdoors.

Pros and Cons of ULV Foggers


  • Cheap to use, no gas cylinders to replace
  • You can control the size of the droplets
  • More versatile as the size of droplets is set by the operator
  • Use less insecticide, making them more economical.
  • Doesn’t heat; reduces fire risk.
  • It can be used indoors with practically no odors.
  • No need to wait for the device to heat up before using
  • It doesn’t create a traffic hazard as the cloud of fog is nearly invisible.


  • Fog is invisible, making it harder to control and keep it away from the operator or bystanders.
  • Produces larger droplets that will stay in the air a shorter time and won’t penetrate the places hard to reach as well as finer droplets
  • It will take more time to treat an area.

Thermal Foggers

  • Propane Fogger

A propane mosquito fogger is easy to use, lightweight, and, as it requires no electricity, it is very portable.

Connect the propane canister, fill the tank with a fogging insecticide, turn on the gas, and press the ignite button. Let the fogger preheat for 2 minutes before using. When ready, keeping the fogger upright, you press the trigger, and a fine mist is expelled.

The propane is used to heat a coil. Then every time you press the trigger, the insecticide passes through the coil. The heat vaporizes the insecticide, the vapor then passes through a nozzle, and on contact with colder air, it condenses and forms a thick white fog.

A propane fogger is for outdoor use as it involves high temperatures that can be a fire hazard. As it’s a small propane cylinder that’s used, this means the fogger is completely portable. You can treat an area of 5,000 square feet in about 10 minutes.

If used near roads a thermal fogger could be a hazard for the traffic due to the dense fog produced.

  • Electric Fogger

Has a similar operating procedure as the propane fogger. The only inconvenience with an electric fogger is the extension cord you have to drag around behind you. Although, there are some battery versions now available.

As with the propane fogger it must preheat for at least 2 minutes before using.

Pros and Cons of Thermal Foggers


  • Slightly cheaper to purchase than ULV foggers
  • The thick fog is easily visible, making it easier to control and safer for the operator and any bystanders.
  • Produce smaller droplets that stay in the air longer and penetrate foliage better
  • Use a low-concentration of insecticide.
  • Treat an area more rapidly than a cold fogger.
  • A propane fogger is completely portable.


  • Uses fuel, propane, in many foggers to heat the insecticide. This is an additional expense, can produce odors, and can leave oily stains.
  • Cannot control the size of droplets
  • Uses high temperatures, so it can be a fire hazard
  • Can create a traffic hazard if used near roads
  • You have to wait for the device to heat up before using.

How To Choose Your Fogger?

When choosing a fogger, you have a few choices, but the first thing to consider is whether you need a thermal or a cold fogger.

Generally, it’s recommended to use cold foggers indoors due to the high temperatures thermal foggers use, which can be a fire hazard. Although a few thermal foggers are designed for indoor use, as a general guideline, keep thermal foggers for outside use. So if you intend to use your fogger indoors, a cold fogger would probably be the best choice.

If you intend to use the fogger indoors and outside, a cold fogger would be best unless you want to buy a thermal fogger for the outside and a cold fogger for the interior of your house: additional expense but the ideal solution.

Do you intend to use your fogger in your yard and on camping or fishing trips? Then a propane fogger will be best as it can be used without electricity.

The next thing to consider is what you will be using your fogger for.

If it’s for insect or mosquito control, a thermal fogger will be better. The droplet size of 5-20 microns is more adapted for this usage. As the droplets from a thermal fogger are a smaller size, they can penetrate very small areas and stay in the air longer. This increases the chance the fog will come into contact with flying insects, such as mosquitoes.

The fog produced will also be more visible, which means it will be easier to control. You can aim the fogger toward a certain area and can see the fog arrive. Also, it is easier for the operator and any bystanders to avoid contact with the insecticide, as you can see it. A cold fogger produces a hardly visible mist but can be used for mosquito control.

fog produced by a thermal fogger
fog from a ULV fogger

The area you have to treat is another consideration. Treating a big garden will be easier and quicker with a propane mosquito fogger; no extension cord is needed. There are also some battery-operated foggers you could consider.

Although, if you have a few acres of garden, then a backpack fogger would probably be best. You will treat the entire area in one go, no need to stop for refilling. The tanks can contain from 2 to 5 gallons. But, think about how much weight you can carry, the larger capacity when full weighs more. A full larger backpack fogger can weigh up to 70 or 80 lbs.

Cold foggers are good for indoor use for odor control, disinfection, treating mold, in greenhouses, treating plants, or pest control.

What Insecticide To Use With a Fogging Machine for Mosquitoes?

There are many different insecticides. Not all can be used in a thermal fogger, and some are specifically for ULV foggers. Other more versatile fogging insecticides can be used in both ULV and thermal foggers. So you will have to pay attention to the fogger manufacturer’s recommendations and read the insecticide label.

When considering an insecticide for pesky mosquitoes, the chemicals are classified as residual or non-residual. This is important as it’s an indication of how long the insecticide will remain active after application.

As a residual insecticide will remain active after application, this isn’t good for the beneficial insects in your garden. For this reason, residual insecticides are often more suited to indoor applications where having a lasting effect may be required.

Non-residual insecticides are only active for a short time after treatment which is much better for the environment and other non-target species.

Many of these insecticides are toxic to fish and aquatic organisms.

Another consideration is an oil-based or water-based fogging insecticide.

Water-based solutions are generally nearly odor-free, don’t stain, pose less fire risk, and are more environmentally friendly.

Oil-based solutions may have a slight odor that lasts a while; they may leave a stain, they are heavier than water-based insecticides, which means they will stay in the air for less time. On the other hand, as they are heavier than water-based solutions, an oil-based insecticide will be slightly less prone to being blown away.

The active ingredients in mosquito fogging insecticides are either Organophosphates such as malathion or Pyrethroids such as permethrin.

Added to these pesticides, you may find one or two synergists that help the active ingredients to work better.

The EPA states these pesticides shouldn’t pose a risk to human health if used according to label directions.

Some insecticides are ready to use, which means you have less exposure to the product. Others need to be mixed with water.

As well as insecticides, you can also use your fogger to apply a repellent. This can be an all-natural repellent that will create a barrier around your home.

Are Fogging Insecticides Safe For Humans?

According to the World Health Organization, the amount of insecticide used in fogging operations is very small and dispersed widely to kill something very small, a mosquito. So, there should be no adverse effects to someone exposed to these products occasionally.

However, it is recommended to take some precautions when you use an insect fogger. It’s a good idea to wear a respirator mask, gloves, goggles, boots, long trousers, a long-sleeved shirt, and a hat.

Do They Harm Other Wildlife?

Unfortunately, applying a mosquito fog can be harmful to some other insects. It’s important to apply the fog early morning or in the evening when other pollinators are not active. In contrast, application during the day or to flowers attractive to bees can cause damage to the bees and other pollinators. Avoiding the fogging of flowering trees and bushes may help to preserve the pollinators.

There has been some research into the effects on bees where a truck sprayed six of the most widely used mosquito control insecticides toward cages containing bees. There was no mortality of bees. In another test, there were hives in an area with frequent mosquito control and hives in areas of no control. The results were encouraging; they found no difference in mortality rates in both groups.

So, if fogging is carried out in the evenings when the bees are in the hives and other pollinators are isolated for the night, and a non-residual insecticide with the correct dosage to kill mosquitoes is used, there should be very little effect on other insects.

In Conclusion – Is Fogging Effective?

Fogging isn’t a lasting form of mosquito control but it is effective and can give you a mosquito-free zone for at least a few hours. Ideal if you’re having an evening with friends in your garden.

Both ULV foggers and thermal foggers can be used to get rid of mosquitoes.

Mosquito control involves different strategies. The most important is to remove standing water. Water that can’t be removed should be covered or treated with a larvicide. Traps are something else that you could consider, they will help eliminate adult mosquitoes.

Photo of author


Peter spends most of his time outside in his large garden. He has been fighting mosquitoes for a few years trying different traps and repellents without using agressive chemicals.

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