What Are Thermal Foggers and How Do They Work?

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What Are Thermal Foggers?

A thermal fogger is a device you can use to fight pest problems in outdoor areas.

There are three types of thermal foggers:

  1. Propane,
  2. Fuel (other than propane),
  3. Electric foggers.

All of these foggers use heat to vaporize the fogging solution. This creates a dense cloud of fog that penetrates even hard-to-reach outdoor areas such as shrubbery, grass, treetops, and so on. Thermal foggers are often used for mosquito control.

How Do They Work?

As the name suggests, a thermal fogger uses heat to vaporize a fogging solution. In most cases, this liquid is an insecticide. It sprays the solution out of the nozzle of the fogger in the form of a mist or a fog.

Thermal foggers have a storage tank that can hold anywhere from about 1.2 L to 10 L of solution. This container, which holds insecticide or other fogging liquids, is located on the bottom of most foggers. In some foggers, though, this container is within the body of the machine.

The machine contains a pump used to send the fogging solution from the container through the heat assembly, which is located on the front of the fogger. The person operating the fogger initiates this pump by pressing the fogging trigger. For most thermal foggers, this fogging trigger is under the handle of the tool.

  • Propane foggers have a socket for the propane gas cylinder on the back of the fogger.
  • Fuel foggers have a large fuel tank on the side of the fogger.
  • Electric foggers have a power cord that needs to be plugged into an electrical outlet for the fogger to work.

When the fogging solution enters the heat assembly, it goes through a coil that is at a very high temperature. This vaporizes the insecticide from its liquid state. This vapor is then sprayed through the nozzle at the end of the fogger in the form of a thick fog. For electric foggers, the heat assembly uses electric energy to heat the coil while fuel and propane foggers use gas (gasoline or propane) to do so.

Particle Size

Thermal foggers can produce very tiny particles, which range from 0.5 micron to 50 microns, with the majority less than 20 microns. The optimal droplet size range for mosquito control is 10-20 microns.  Particles this small will stay in the air for a long period of time before falling to the ground. The tiny particles will also be able to get into hard-to-reach places both indoors and outdoors.

Most ultra-low volume (ULV) foggers allow you to adjust the particle size produced. These can go from as low as 2 microns up to 50+ microns in size by adjusting the airflow of the fogger. Most thermal foggers, on the other hand, produce a wide range of droplet sizes during application. It’s difficult to make a thermal fogger produce droplets of one consistent size.

Thermal Fogger Use

Thermal foggers are the preferred tool for outdoor fogging. The majority of thermal foggers are for outdoor use only.

Since thermal foggers work with high temperatures, they aren’t safe for indoor use. This is especially true if there are flammable materials around.

Also, if the fogger’s heat assembly hasn’t reached the correct temperature before you start to fog, the insecticide can start to drip from the fogger. This will leave hard-to-clean stains on the ground, which is another reason why it’s not advisable to use thermal foggers indoors.

The fog produced by a thermal fogger is thick, white to gray in color, and is easily visible. This gives you better control over the areas you’re fogging. With a cold fogger, the fog produced is transparent and odorless, so it’s harder to see the places the fog is reaching. This is especially noticeable when fogging an outdoor area in windy conditions (which is not recommended; wind can blow the insecticide far from your target).

Thermal Fogger Prices

The price for a thermal fogger can start at around $50 for the most basic version. It can reach $1000+ for professional foggers equipped with powerful electric motors and large capacity tanks. These are used in industrial areas as well as in many tropical countries to control mosquito-borne diseases.

For comparison purposes, the price of a cold fogger will start at around $200. This price can also grow to nearly $1000 for the professional models used in large indoor areas such as commercial buildings and warehouses.

In addition, most propane foggers don’t come with a propane cylinder. So, you must buy this separately. The price of these cylinders is about $10 or less, though. You can use thermal foggers with different pesticides and insecticides, based on the type of pest problem you need to solve.


peter van Leeuwen

can a cold fogging soln be in a thermal fogger


    It depends on the fogger and the fogging solution you have since there are water and oil-based fogging liquids and foggers that work only with either the oil or water-based liquid or with both. So, check and see what solutions can your thermal fogger be used with and then see if your fogging solution meets those specifications.


Which are the specific types of forger and fogging solution used for weed control


    Since we’re focusing on insect control rather than gardening, I’m not competent to give you advice on weed control. However, the market offers products that already come with nozzles, so you could try looking into those.


What type of fogger would you advise for mosquito control, and to be used in a warm country for a small starting pest management company ?
Thanks ahead.


    Hi! Congrats on starting your own business. As for the fogger, I suggest you consult someone who is in the business since we mostly focus on giving advice to people who seek it for personal use.

Dessie Williams

Can the thermal fogger be used for disinfecting businesses impacted by the coronavirus?

    Kristiana Kripena

    Thermal foggers can be used for disinfecting businesses, however, for indoor use, we recommend using a cold or ULV fogger. You can learn more about this in our article about using foggers for disinfection.

Gbenga Majekodunmi Samuel

I have a thermal fogger which is can be use for cold fog as well.

What solution of disinfectant is best to use for decontamination of an office area bearing in mind that I don’t want an explosion to occur.

Secondly, I cannot get any EPA approved disinfectant currently because of the pandemic. How can I produce a compatible composition of disinfectant for thermal fogging


    We mainly focus on all things pest-control, therefore, we won’t be qualified to give you info about disinfecting. We suggest asking for advice to someone closer to the cleaning field since they will probably know what solutions will work to keep your environment safe from viruses.

Cherrypie Nisnissan

Is it dangerous to use a flammable solvent like White spirit in a Thermal fogger ?


    Generally speaking, it’s prohibited, and we would strongly suggest against it. Though, you can try looking up your specific device to see what its label says about the matter.

William Huskey

Do you remember a thermo fogging solution called three & one kill selling back in the 60s and 70s the best thermo fogging solution I ever used I fogged a house infested in roaches after I fogged the house there was a one inch high carpet of dead roaches it took about five minutes to fog

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