Thermal vs. Cold Foggers: Advantages and Disadvantages

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Thermal and cold foggers are two different types of devices used for the same purpose: insect control.

In this article, we’re going to look at the advantages and disadvantages of both thermal and cold foggers. Let’s start with thermal foggers.

Thermal Foggers: Advantages


The thick, visible fog

One of the major advantages of thermal foggers is the fog itself. Since thermal foggers use heat to vaporize the fogging solution, it forms a thick cloud of fog that can be white or grey. ULV foggers that use cold fogging techniques, on the other hand, produce a practically invisible fog.

A highly visible fog has a few advantages, such as:

  • It’s easy to control and monitor the flow of the fog. For many applications, you’ll need to control and direct the fog to reach certain areas, such as the foliage of plants, treetops, and other areas. Since the fog produced by thermal foggers is highly visible, it’s very easy to aim the fog towards certain areas and see that it hits its target.
  • If you are an operator, the visible fog provides peace of mind to your clients who can actually see you doing something to combat their problem.
  • It’s easier for the fogger operator to avoid direct contact with the fog. This is also true for bystanders. Since the fog might contain substances that are not good for your health, being able to see it makes it easier to avoid.

Smaller droplets and a higher droplet density

The droplets produced by thermal foggers are very small and can even get as small as 0.5 micron in diameter. Because of the small droplet size, these foggers produce, they can spray a higher density of droplets. Both of these factors make thermal foggers perfect for insect control applications.

The particles produced by thermal foggers can penetrate very small areas. In outdoor applications, the smaller particles will stay in the air for a longer amount of time. This will increase the chances that fog will come in contact with flying insects such as mosquitoes.

Can use water- or oil-based solutions

Thermal foggers allow you to use both water and oil-based solutions. Water-based formulations are a lot more environmentally friendly, can be used to fog plants, and don’t pose a fire hazard. Furthermore, water-based solutions don’t cause equipment corrosion and are cheaper than oil-based solutions.

More efficient

Thermal foggers are more efficient than cold foggers in a few ways. They can:

  • Use a low concentration of the insecticide.
  • Spray more insecticide using less energy than ULV foggers.
  • Treat an area of the same size in a shorter amount of time than cold foggers can.

Thermal Foggers: Disadvantages

Use a lot of fuel

Possibly the biggest disadvantage of thermal foggers is that they use a large amount of fuel. In most personal-use foggers, this is propane gas. Thermal foggers have to use some sort of fuel to heat the heater assembly and this has some drawbacks, such as:

  • The high cost of the fuel used in thermal foggers. You’ll have to refill or change these when they run out, which can happen pretty often if you need to fog larger areas. This can make the fogging more expensive.
  • The fuel can have a strong odor that may be unpleasant for the person operating the fogger and other people in close range.
  • These substances can leave oily stains that are hard to clean, which is a problem for indoor fogging.
  • Propane is flammable.

Traffic hazards

Because of the dense fog they produce, thermal fogging can cause traffic hazards. This is especially true when using high-capacity professional thermal foggers.

Fire risk

Thermal foggers work with very high temperatures. This means that the heater assembly part of the fogger can get very hot while in operation and so using the fogger can cause serious fire risks (as well as burn risks to operators if improperly handled).


A high-capacity, powerful, professional thermal fogger will be very loud when operating. This can limit the use of that fogger in urban areas.

Small droplet disadvantages

Small droplets have significant advantages over larger particles when it comes to mosquito control. But there are also some disadvantages to smaller particles.

The biggest disadvantage is that they can be easily moved in any direction by smaller wind gusts. This will make fogging in windy conditions more difficult.

Cold Foggers: Advantages


Use less fogging liquid and fuel

Ultra-low volume (ULV) foggers, as the name suggests, use a low amount of fogging liquid. This results in a lower cost of application. A ULV fogger uses air pressure to atomize the fogging solution into very small particles.

Cold foggers also use electricity or battery power instead of propane fuel. This means that the disadvantages of fuel use that apply to thermal foggers don’t apply to cold fogging devices. The advantages of this include:

  • They are cheaper to use since you won’t need to buy additional fuel.
  • They won’t produce any hard-to-clean oily residues.
  • Low fire risk and virtually no burn risk to operators.
  • ULV foggers are practically odorless on most occasions. This makes them much more pleasant to use, especially indoors.

Can use water- or oil-based solutions

Like thermal foggers, ULV foggers can be used with water or oil-based insecticide preparations.

No traffic hazards

Cold foggers produce a practically invisible cloud of fog. This won’t cause any traffic hazards, so you can use this type of fogger in cities and other crowded places not only for pest control but for disinfection or sanitization purposes as well.


Electric ULV foggers are generally quieter than thermal foggers, which is useful in urban areas where noise may be an issue.

Cold Foggers: Disadvantages

A practically invisible fog

The fog produced by a cold fogger is practically invisible. This has its advantages, such as avoiding traffic hazards but also has some disadvantages. First of all, it’s much more difficult to monitor and control the direction of an invisible fog, especially when fogging outdoors. This is a disadvantage for mosquito control applications.

For example, if you’re fogging outdoors with some wind, the fog will drift away from your target area. With the visible fog from thermal foggers, you can easily observe this and try to correct it by more precise application. With a cold fogger, on the other hand, you won’t be able to see where exactly the fog is drifting to, so it’ll be much more difficult to direct it to a certain area.

Also, bystanders won’t be able to see any signs of fog. This means they won’t be able to avoid it and might inhale insecticides or get them on their skin.

Difficult to maintain and repair

Cold foggers require greater technical skills and are more difficult to maintain and repair. They have an electric motor, air pressure pumps, and complex nozzles that will need to be both calibrated and repaired by a trained professional.

Larger droplets

ULV foggers produce larger particles than thermal foggers. These usually range from 10–50 microns in diameter. While you can adjust the size to fit different applications, a cold fogger simply can’t match the high-density, small droplet output of a thermal fogger. In indoor and outdoor applications, this means that the fog won’t be able to penetrate the smallest and most difficult to reach places. For mosquito control, larger particles will stay in the air for less time and won’t have as great of a chance of reaching all of the airborne mosquitoes in the area.


Cold foggers will need more time to fog a similar-sized area than a thermal fogger would due to the smaller volume of insecticide and fog itself.


Steve L. Wood

Conventional sprayes, reach insects less effectively than ULV technology. This is because conventional sprayers spray larger droplet sizes in between 100-200 microns, which don’t fully cover the whole area being sprayed. Apart from the droplet size they produce, manual sprayers can be very time consuming and labour intensive. Although motorized versions spray quicker, there are not suitable for indoor use, as they leave surfaces very wet and produce exhaust gases. Manual sprayers are ideal when you need to pray close up, in places such as patio areas and gardens.

Lloyd Pitts

I plan to use a pressure washer. The spray can reach high in trees. What do you think of that?


    I wouldn’t advise you to do so, since pressure washers can be a lot for trees to handle. I also don’t think it’s a great idea to put an insecticide in one, considering coming in contact with an insecticide can be harmful, for example, to your own health. You can use a garden hose, since the pressure in those is a lot smaller, which makes it safer.

David M Rifenbark

We are certified organic, we use alot of botanical insecticides, which would be better for applying these botanical extracts hot or cold?


    Cold fogger or garden sprayer would probably be a better option for you.

Mike Fa

Thank you for a very informative article . I hope you can help with more clarification on the 2 types of fogger so i can decide on whether i should invest in a thermal fogger or a cold fogger, to fog my 2,500 sf x 5 feet tall attic crawl space on an annual basis to eradicate and stop termite infestation?

    Kristiana Kripena

    Most termite-specific products are usually applied using a simple hand pump sprayer. But if you really want to get a fogger I’d go for a cold fogger if your intent is to treat a termite infestation. Additionally, cold foggers are also generally safer for indoor use.


Which one is better to disinfect an office where there are files, paper etc?


    When it comes to indoors, we would generally suggest using cold foggers, considering the fire hazard that comes with thermal foggers, as well as you’ll be avoiding the staining. Still, keep in mind things might get wet, therefore, get damaged.

Amith Ramdeo

Hi, i am trying to make an informed decision on which to go with. ULV or thermal. I intend on sanitising my office park of about 70000sqm. Keeping in mind that no paperwork will be removed from any space within the buildings.


    You should pick a ULV fogger. They are a better fit for disinfecting, as well as better for indoor use, as thermal foggers are considered a potential fire hazard.

Elmar Landman

What will work the best for classrooms and homes, started a new venture and want to know which one will work the best


    For indoor use, we would suggest going for a ULV fogger. As for more specific reasons and considerations, you can re-read the article, to see the pros and cons.


We intend to buy a fogging machine for external use in our Apartment Building and internal use (Indoor use) i.e.inside the apartment both. After reading your above article, I am of the view that for external use we must buy a Thermal machine and for internal use we must buy a Cold ULV machine.Please give your views and suggest. Thank you!


    If you want the same fogger for both indoors and outdoors, we suggest a ULV fogger. Thermal foggers shouldn’t be used indoors, as they cause a fire hazard. But you have to keep in mind that controlling and monitoring the fogging process with it will be harder. You also need to pay more attention to the weather conditions (e.g. it shouldn’t be too windy when you fog). Also, keep in mind you won’t be seeing the fog from the ULV fogger. Other than that, it can still be used outdoors as well.
    However, if you’re fine with buying both kinds, that, of course, would be the best-case scenario.


Hot fogger is the best one for insect s. Hot fog is light weight smoke

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