Insect foggers can be categorized into two large categories: ULV foggers (cold foggers) and thermal foggers. You may have come across one or both of these terms when browsing for insect fogger products. While the purpose of both types of fogger is the same, they actually use pretty different fogging techniques and require different types of fogging liquids.


Thermal foggers, as the name suggests, use heat in the fogging process. Thermal foggers use this heat to vaporize a fogging solution and spray it out in the form of fog. Thermal foggers are equipped with a heat barrel that is preheated to high temperatures using either propane gas or electricity, depending on the type of fogger. The liquid fogging solution is then is pumped into the thermal fogger’s heat barrel where it is instantly vaporized. This allows the fogger to produce a large amount of extremely small particles which altogether form a dense cloud of fog.

As mentioned, there are two types of thermal foggers: gas and electric. They are pretty similar when it comes to appearance, but gas foggers require a gas cylinder (usually propane) to be mounted to the fogger. Electric foggers, on the other hand, need to be plugged into an electric outlet. Gas powered foggers are cordless, fully portable, and can be used anywhere while electric foggers are subject to the length of their electric cable or extension cord. Gas foggers have larger operational costs because when the gas cylinder empties, it will need to be changed and will cost more than the electricity an electric fogger consumes.

The opposite of a thermal fogger is an ultra-low volume (ULV) fogger, a cold fogger which operates using a distinct fogging technique. To produce a fog with small droplets, ULV foggers are equipped with motors that produce a high power, low-pressure air stream. As with thermal foggers, the fogging solution is stored in a tank and the fogging liquid is pumped out of the tank when the fogger is in operation. The solution is then pumped into a special nozzle that is designed to cause the airflow to move in a swirling motion.

The high air pressure produced by the motor helps to spray the fogging liquid through the nozzle and separate it into tiny particles. The liquid solution is sprayed out of the nozzle in the form of a fog or fine mist. ULV foggers mostly use electricity to power an electric motor. The particles size that ULV foggers produce can be adjusted, allowing you to use the fogger for different applications. Also, because ULV foggers use cold fogging techniques and are not heated to high temperatures, they can be used both indoors and outdoors.

Particle Sizes

The particles produced by thermal and cold foggers will vary in size based on the model of the fogger. Thermal foggers will generally produce particles that are smaller in size, averaging 0.5-10 microns, while ULV foggers will produce particles that are a bit larger in size, 5-30 microns on average.

Average particle sizes in microns

The heating technique that thermal foggers use allows them to produce extremely tiny particles which can penetrate very small areas both indoors and outdoors. Insecticide or other solutions are vaporized to produce a dense, thick cloud of fog. The fog produced by a thermal fogger is easily visible, which, in turn, allows the direction of the fog to be controlled more easily. While a thermal fogger can produce extremely small particles, their size is inconsistent. This means that the particles produced will vary dramatically from 0.5 to 30 microns in size.

Different ULV foggers will produce different sized droplets. ULV foggers can produce a very consistent particle size which can be varied by adjusting the flow rate. This is especially useful if you need to fog different areas or to use the fogger for various purposes, such as for getting rid of mold, removing unpleasant odors, or killing insects and other outdoor pests. ULV foggers also need less diluent so they can produce a more concentrated fogging solution. This, in turn, can make some types of chemicals cheaper to use.


Thermal and ULV foggers have similar uses in many aspects. Both devices are generally foggers or misters that are used to spray either a water- or oil-based fogging solution. Both types of foggers are used for insect control, odor, and mold control applications in indoor areas as well as to disinfect, to apply pesticides, to getting rid of pests in warehouses, and for other similar uses.

There are other areas where thermal foggers are better suited than ULV foggers and vice versa. Thermal foggers have the advantage of producing particles that are a smaller size than ULV foggers with a fog that is more easily visible. This makes them better for such applications as:

  • Mosquito and insect control: The small droplets that a thermal fogger produces are good for controlling mosquitoes and other smaller insects. For mosquito control, the best droplet size is from 5-20 microns. Most thermal foggers will produce particles within this range.
  • Controlled outdoor fogging: As the fog that a thermal fogger produces is thick and easily visible, you can control the direction of fogging with more ease. This will allow you to better control your outdoor fogging as most ULV fogging devices produce a barely visible fog.
  • Fogging obstructed areas: Due to the small particle size, the fog produced by a thermal fogger can penetrate very small places such as gaps in floors, cracks in walls, and similar places indoors. It can also work its way into thick bushes, long grass, high treetops, and other hard to reach places outdoors.

ULV foggers, on the other hand, do not use extensive heat in the fogging process. This allows them to be used indoors without fire risks. Also, ULV foggers produce an almost invisible fog and allow users to adjust the particle size, so they can be used in more applications than thermal foggers. ULV foggers can be used:

  • In any indoor place: As mentioned above, ULV foggers use a cold fogging technique, so they are safe to use indoors.
  • For odor control and disinfecting: ULV foggers are often used to disinfectant houses and large warehouses as well as to control unpleasant odors in such areas. ULV foggers can be left to work automatically and there is no need for someone to operate the fogger at all times as is the case with thermal foggers.
  • To get rid of mold: ULV foggers can also be used with special chemicals to get rid of mold in indoor areas.
  • On plants and greenhouses: Because ULV foggers allow you to adjust the particle size, they can also be used outdoors or in greenhouses to spray different solutions on plants.
  • Indoor and outdoor pest control: ULV foggers are the best pest control method for indoor areas. They can also be used outdoors to control mosquitoes, for example. Even though ULV foggers cannot produce as small of particles as thermal foggers, some ULV foggers can produce particles in the 5-20 micron range, which is effective for mosquito control. One disadvantage of using a ULV fogger outdoors is that they produce an almost invisible fog, so it will be harder to control the direction of the fog.