Thermal Fogging Machines vs ULV Fogging Machines

Differences, Uses & Comparisons

If you have been browsing to buy a fogging machine in South Africa then you will likely have noticed there are two main variants on offer, Thermal Foggers or ULV Foggers, but if you haven't been in the pest extermination business or fogging application business before then this might have brought about some confusion as to what the differences are. Knowing what types of foggers you can use to decontaminate, disinfect or exterminate is vital and hopefully, the following information will ease your decision and allow you to find the right fogging solution!

Whether you are looking for a fogging machine because you want to be extra safe and sanitised after Covid-19 (coronavirus) hit, or if you are perhaps considering purchasing fogging equipment and chemicals to start your own fogging business then we hope the following explanation and review on the differences between ULV (cold) foggers (such as our Viru Fog or Sani Nova) and thermal (hot) foggers (such as our Red Bird or Blue Bird) will provide you with an answer and enable you to make the best decision.

Let's Take a Look at the Main Comparitive Differences.

Although the purpose of both types of fogging machines is the same, they use different fogging techniques and sometimes require different types of liquid fogging solutions. However, our chemical solutions (supplied by Dyna Fog Africa / SaniChem SA) are designed to be used in both thermal or cold foggers and work fantastic at a wide range of temperatures.

How do Fogging Machines Work?

Thermal foggers, as the name may give away, produce heat. A thermal fogger will heat up a coil inside a metal tube, causing the liquid solution to vaporise or atomise. This heated or atomised solution is then pushed out the tube as a vapour, or what we call a fog, in a visible cloud made up of thousands of droplets. The heating method for thermal foggers comes from petrol or in some cases electricity. Our thermal fogging machines use only petrol and a compression engine, which features less moving parts than combustion engine thermal foggers, making them less likely to break or require maintenance. They also feature a battery for the spark and electric, push-button, starter.

Generally these petrol foggers are more expensive due to the consumption of fuel, but for the same reason these foggers are ideal for applications where power sources are not within reach or perhaps the unfortunate but frequent occurrence of loadshedding in South Africa. The fog produced is also smaller and produces a white "smoke" which gives the user the advantage of being able to see where their fogging solution is being applied.

ULV (or Ultra-Low Volume) Foggers, Also Called Cold Foggers, Do Not Use Heat to Atomise the Fogging Solution. Instead, They Produce Fog Using Pressure in One of Two Ways:

  1. The chemical solution is pumped through a high-pressure nozzle
  2. The liquid is slowly sent through a vortex of high-speed air

This pressure or high-speed vortex method breaks up the liquid into micro droplets, which then spray out as an almost invisible fog.

With a ULV fogging machine you can usually adjust the size of the droplets, which makes it great for a variety of applications and small indoor environments. Without the petrol or heat (fire risk) ULV foggers are also safer for indoor use. ULV foggers are also quieter and thus appeal more to the hospitality and medical industry.

Droplet sizes of fogging machines:

One of the biggest differences between ULV foggers and Thermal Foggers is the size of the liquid droplets which are released.

Our ULV Foggers usually push out droplets between 5 and 50 microns

Our Thermal Foggers produce droplets from 0.5 to 50 microns

Thermal Fogging vs ULV Fogging Micron Size:


An important consideration when looking at the size of the droplets is how long the particles will float and travel for. More "air-time" for the chemical solution means more time to kill flying insects and airborne viruses.

Smaller droplets are lighter, meaning they will hover around in the air for longer and reach more areas and tight spaces easier. This also means that smaller droplets will travel further with wind and spread further.

Larger droplets, such as those produced through ULV foggers, will be more direct when sprayed and less affected by wind. These droplets will settle faster and are still small enough to reach spaces easier than conventional methods of sanitising or decontaminating.

The diameter of the droplets can usually be adjusted through electric ULV foggers but cannot be adjusted through thermal fogging machines, however, their overall smaller droplet size means they are more likely to penetrate areas where the ULV foggers cannot, such as dense foliage, tight corners etc.

Another consideration here is that ULV foggers, as their name suggests, use ultra-low volumes of chemical solution. This means they are usually more environmentally friendly (under certain applications such as insecticide) but also has the disadvantage of making them slower when wanting to fog indoor spaces quickly and efficiently.

Overall both types of machines have their advantages and disadvantages, meaning that when considering which fogging machine to choose, you will need to look at what you will be using the machine for. Generally, these are the application areas that best suit each type of fogging machine

Thermal Fogging Applications:

One of the biggest differences between ULV foggers and Thermal Foggers is the size of the liquid droplets which are released.

  • Insect control (especially flying insects such as mosquitoes): For insects which transmit viruses and diseases to humans (insect vectors which transmit vector-borne diseases) a droplet size of 10-15 micron is recommended. Since thermal fogging machines produce the smallest droplet sizes and cover this range, the droplets will remain airborne for longer allowing them the needed time to kill the target while also being able to reach through dense, bushy areas where larger droplets would not.
  • Outdoor pesticide applications: A big advantage of thermal fogging machines is the dense visibility of the fog. This essentially means the operator has added control over where they are directing their chemical solution. In cases where harmful pesticides are used, being able to watch where you fog is a big advantage.
  • Small and hidden spaces: The smallest droplet size means the best possibility of reaching all areas. The solution will be ables to flow into cracks and crevices in ceilings, floors and walls where pests may hide, as well as dense foliage such as between blades of grass and thick bushes.
  • Indoor disinfectant applications: With the recent outbreak of Covid-19 these thermal fogging machines have often been utilised for indoor applications. Again, the smaller droplet size and the lack of cables or need for electricity outlets nearby makes them great for quick and effective applications in warehouses, halls, shopping malls and other large indoor areas. However the noise and fire hazard does need to be considered for areas which may not allow excessive noise or fuel on site (such as hospitals, harbours etc.)

ULV Fogging applications:

ULV fogging with Sani Nova

ULV foggers have an adjustable flow rate or droplet size (bigger drops means more chemical solution being dispersed), do not use petrol and heat (low fire hazard) and are quieter than their thermal fogger counterparts, making them best suited for:

  • Indoor spaces: Being much quieter and less of a fire hazard, ULV foggers are often used for indoor applications. The adjustable droplet size also helps with being able to directly cover a specific area.
  • Disinfecting and odour control: Since they are great for indoor applications and because they use electricity, these machines are ideally suited for disinfecting and decontamination. For outdoor areas or where electricity is not readily available, a thermal fogging machine would be best suited.
  • Mould and fungal control: ULV machines are more frequently used for mould and fungal control indoors with the ability to directly apply a chemical solution at an adjustable rate.


Although both machines can be used for the above applications, there are areas in which the one or the other is better suited. This is where the decision will come in depending on your specific needs. There is no clear winner, however, here are the main points to be considered.

Thermal Fogging Machines:

  • Visible Fog
  • Smallest Droplet Size
  • Use Fuel and Heat
  • No Need For Plug Points or Extension Cords
  • Produce Loud Noise
  • Work Faster Than ULV Machines

ULV Fogging Machines:

  • Adjustable Flow Rate / Droplet Size
  • Quieter Operation
  • Smaller and Easier to Operate
  • Use Electricity and Pressure
  • No Combustable Fuel
  • Require Plug Points / Extension Cords
  • Use Less Chemical Solution
  • Take Longer to Apply

Hopefully this will help make your decision a bit easier when buying a fogging machine. If you still need more assistance then please feel free to contact us.

Don't forget to view the fogging equipment we have for sale, we cater to all industries and sizes and if you are looking for the best fogging chemicals then look no further than our range of SaniChem SA and DynaFog Africa products.