The Differences Between Thermal and ULV Foggers

Insect foggers can generally be categorized into two large groups:

  1. ULV foggers (handheld cold foggers or the more practical backpack foggers)
  2. Thermal foggers.

You may have come across one or both of these terms when browsing for pest control products. 

While the purpose of both types of fogger is the same, they use different fogging techniques and require different types of fogging liquids. And when talking about cold foggers you can make the decision to buy a handheld fogger or more practical backpack fogger. 

Operation

Thermal foggers are so named because they heat up a coil within a metal tube, causing the liquid insecticide solution to vaporize. They then propel this vapor (composed of hundreds of tiny droplets) out in a visible cloud. The heat for thermal foggers comes from either propane or electricity

As mentioned, there are two types of thermal foggers:

  1. Gas thermal foggers – require a gas cylinder (usually propane) to be mounted to the fogger.
  2. Electric thermal foggers – use electricity or batteries.

Gas and battery-powered foggers are cordless, fully portable, and can be used anywhere, while some electric foggers are subject to the length of their cable or an extension cord.

Propane foggers are more expensive due to the consumption of gas instead of electricity.

ULV (ultra-low volume) foggers, also called cold foggers, don’t use heat. Instead, they produce fog using pressure in one of two ways:

  1. Either the insecticide solution is pumped through a high-pressure nozzle
  2. or the solution is slowly sent through a vortex of high-speed air. The pressure breaks up the liquid into tiny droplets, which then spray out as an invisible fog. 

The motors are typically powered by either electricity or batteries but some models use gasoline. Operators can adjust the size of the droplets produced by ULV foggers, allowing for different uses. The lack of heat (and thus fire risk) makes ULV foggers safer for indoor use.

Particle Sizes

Droplet sizes vary by model.

  • Thermal foggers generally produce smaller droplets, with a minimum diameter of 1 micrometer.
  • ULV foggers typically produce slightly larger droplets, with a minimum diameter of 2 micrometers.

Average particle sizes in microns

Because thermal foggers produce such small droplets and visible fog, they are ideal for outdoor applications. Smaller droplets hang in the air longer, increasing the likelihood that they will contact a flying insect.

Furthermore, tiny droplets penetrate dense foliage better than larger droplets. Visible fog is easier to monitor and control than invisible fog, allowing for greater efficiency.

However, because the droplet diameter cannot be controlled in thermal foggers, their size can vary dramatically, which somewhat reduces their efficacy.

ULV foggers, on the other hand, produce more precisely sized droplets that can be varied by the operator. This provides versatility not available in thermal foggers.

And, as their name suggests, ultra-low volume foggers use less insecticide, making them more economical and slightly more environmentally friendly.

Uses

Thermal and ULV foggers have similar uses in many aspects. Both can spray either a water or oil-based fogging solution

In addition to pest management, both can be used to disinfect rooms and control odors, mold, and fungus indoors and outdoors.

However, in some situations, one or the other type may be better suited.

Thermal foggers generate smaller droplets in a visible fog, making them ideal for such applications as:

  • Insect control (including mosquitoes): For control of insect vectors (insects that transmit diseases/viruses to humans), the optimal droplet size is 10-15 micrometers, well within the range produced by thermal foggers. As mentioned, smaller droplets remain suspended longer and penetrate dense vegetation better than larger droplets.
  • Directed outdoor applications: The visibility of the fog produced by thermal foggers allows for operators to monitor and control the direction of the spray.
  • Small, hidden areas: The small droplets produced by thermal foggers are ideal for depositing insecticide in cracks and crevices in floors, ceilings, and walls, as well as dense thickets and other foliage.

ULV foggers, on the other hand, don’t heat up, reducing the risk of fire. Furthermore, the invisible fog makes them better suited for neighborhoods and military encampments, where visible “smoke” could cause alarm. They are also quieter than thermal foggers.

ULV foggers can be used:

  • Indoors: As mentioned above, ULV foggers do not heat up and can be used inside.
  • Disinfecting and odor control: ULV foggers can be used to disinfect indoor spaces and can be operated remotely.
  • Mold and fungal control: Mold control solutions and fungicides can be applied using ULV foggers indoors as well as on crops (in greenhouses or gardens).

39 Comments

kalpana

Dear Karen,
Can I use outdoor cold fogging solution ( to be mixed in water) in a sprayer(as fogging machines are very expensive) What results will I get.

    Karen

    Hi Kalpana.
    You can use cold fogging solution in a sprayer, however there are few disadvantages when compared with cold ULV fogger which you need to be aware of:
    1) A regular sprayer cannot atomize fogging solution in such small particles as ULV fogger so it won’t cover as much area and won’t be able to penetrate smaller gaps and holes because of the larger particle size.
    2) Most cold ULV foggers have pretty powerful electric motors so they can output solution in much greater distances than hand sprayers, but this won’t be a problem if you need to fog a small area.
    Other than that, you can use a cold fogging solution in a sprayer.

    Let me know if you have any other questions.
    Regards, Karen.

    Kalpana

    Dear Karen
    Thanks for the prompt reply and very helpful answer.Please let me know what is the difference in solution /contents used for outdoor cold fogging vs indoor cold fogging.

    Karen

    Hi Kalpana.
    Glad that my previous answer was useful to you!
    As for your question, I think that the main difference between outdoor and indoors cold fogging solutions is their content. If you want to fog an indoors space chances are that it will be your home or a place where you spend a lot of time so you should look for a solution that is more natural and isn’t as potent, because it will be safer for you as well as it will be easier to air out the space after fogging. A good option is Pyrethin based solution diluted with water.
    But for an outdoors space a solution you can either simply use a Pyrethrin based solution, because it is natural enough so that you can spend time in the sprayed area soon after fogging but it will still kill all of the mosquitoes, or really any other solution that is meant for cold fogging in outdoors environment, because outside you don’t have to worry too much about residue or airing out the space.
    Hope this helps!

    Regards, Karen.

    kalpana

    Thanks for the info! Really very helpful.

    Jane

    I am looking to use a fogger to help control or get rid of bird mites in my home. I am looking at Kleen Green Natural Enzyme as it is not toxic. Spraying the entire house using a hand spray bottle is not practical. However, the Kleen Green is only effective while wet and leaves no residual effect. Would it come out of the fogger wet enough to help? I would appreciate some advise in this. Would using a humidifier be a better solution? I would rather use a fogger if this would work. Thank you.

    Karen

    Hi Jane,
    I agree that spraying the whole house with the Kleen Green Natural Enzyme using a hand sprayer bottle isn’t practical, however, since the label says that the product needs to be applied wet and then wiped off, I am not sure that using a fogger would be your best course of action. I would suggest getting a manual pump sprayer, like this one for example, that will still distribute the product wet, but at higher rates than regular spray bottles, so it will be much easier for you to spray your whole house with the product in small amount of time.
    Best,
    Karen

Moe

that’s really helpful
thanks!

Worth

I’ve been researching thermal foggers for use around my home this spring and summer for mosquitos, biting gnats and biting flies. I live on about 30 acres surrounded partially by a swamp. I anticipate fogging about a 5 to 10 acre area with the fogger on the back of a utility vehicle. I will be fogging around my home and a three acre pond that I occasionally fish and we eat the fish. So I need something efficient and environmentally safe. I am looking at several models/brands in the 2-3 thousand dollar range(hopefully 2).

Any suggestions would be helpful. Would you suggest water or oil based for the pond? What size should be adequate? Is there a particular brand/company that stands out? thanks

    Karen

    Hello.
    First of all, let’s start with the pond. In general, there is no difference whether you use a water or oil-based product when it comes to fish, what matters is the active substance used in the solution, some of these substances can be very harmful to fish while others are less. The important thing is to always read the label and gather as much information as possible of the insecticide you are going to use. In general, insecticides advertised as bio or natural are going to be less harmful to fish.

    Another thing when comparing oil and water-based solutions is that oil insecticides are going to provide a longer effect because they last for much longer time on the fogged surface than water-based solutions, which is great for mosquito control. Oil-based solutions can also be applied in more windy conditions.

    However, when we consider the safety of the environment, water-based products are better because they evaporate faster, which, for example, is better for fish, because they stay in contact with the chemical for much less time.

    When talking about foggers there are few great options available, ones that can output water-based solutions, oil-based, or even both. You have done good research to choose thermal foggers because practically all of them can output particles at 5-30 micron size, which is the most effective for insect control. From companies, I would suggest either VectorFog or Curtis Dyna-Fog, both of these make the highest quality thermal foggers for large area fogging.

    From foggers that can output oil-based solutions I can recommend this: Golden Eagle fogger by Curtis Dyna-Fog

    And there are also some high-quality foggers that can output water and oil-based solutions such as the Vectorfog H200SF Portable Thermal Fogger and the Curtis DYNA-Fog Trailblazer Fogger.

    Worth

    Thank you. Your response was very helpful, more thorough then I expected. Worth

vicky

Ratio of cedarwood oil and hydrated silica use in fogger machine to rid off from mold. Can I use thermal fogger to make fog of cedarwood oil and hydrated silica or cedarwood oil and ethyl lactate. Pls suggest.

Your advice will help to make one house mold free.
Thanks

    Karen

    Hi Vicky,
    Well it depends on what type of solution you are using.
    If you are referring to a store bought product like the Wondercide Natural Indoor Pest Control Spray for example then you should check the label of that products and see what it says, since it should be stated there what type of application this product is suitable for (in the case of the previously mentioned Wondercide spray, the label of it clearly says that it is suitable for spray or fog application).
    But if you are mixing the ingredients yourself, then you need to see if your fogger is suitable for them. As long as your fogger can be used with oil based solutions, since you are mixing cedarwood oil with other ingredients, it should be fine to use the solution with you fogger machine to make your house mold free.
    If you have any more questions, don’t hesitate to use the contact form on the website to contact me directly!

    Hope this helps!
    Karen

paul sadiku

Hello, quite interesting questions and answers, i’m to work on a vessel (ship) and also industrial office spaces. I am buying ULV Cold fog for the vessels/plateform and a thermal fog machine for out door uses. I reside in tropical countries (Nigeria, Africa).
1. can this machines serve pest cointrol in this region
2. can the solution used for thermal fog machine be used for the ULV COLD FOG
3. If i am to used a ULV COLD FOG what is the solution quantity i will use to fumigate a building of 30m*30m and the height is 15m

    Karen

    Hi Paul,
    To answer your questions:
    1. Both the ULV and the thermal fogger will be useful for pest control, especially in tropical countries. You just have to make sure that you get a fogging solution, that is suited for the pests that you want to combat.
    2. It depends on what solution it is. There are some that can be used with both and some that are suited for only one type of fogger. I would recommend to check the label of the solution (on the solution bottle or on the Internet) and see what type of fogging machines it is suitable for, since that information should be mentioned somewhere.
    3. Again, it depends on the solution and this information should be mentioned on the label or in the user guide if it has one. If not then I would say a gallon of solution should be enough for a 30 by 30 meter since the space isn’t that large, especially if it is an indoors space. Just remember to also check if the solution you buy can be used indoors, since there are some that can only be sprayed outdoors.

    If you have any more questions, don’t hesitate to use our contact form on our Contact Us page, to contact me directly.
    Best,
    Karen

Brajesh

Hi karen
It is very knowledgeable questions and answers done by you. I have one little question, that what is the quantity of insecticides in ulv fogger sprayer in outdoor if I used 500ml of any Insectiside in 200 litter of water for one acre of land by knapsack sprayer, if I using ulv sprayer it consume only 20 litter of water for one acre. So what is the quantity of insecticides for ulv fogger .

    Karen

    It depends on the insecticide you are using. Instructions and the insecticide to water proportions should be noted on the label of the insecticide.

Chris

Hi Karen,

My wife and I have a small barn with cows that have attracted an absurd amount of flies on the property that are taking over. I bought a cheap propane fogger that only recommends an insecticide with little A.I. Can I use a higher concentration, and will it help, or is the low concentration ok. Also is there any insecticide that you would recommend that targets house flies, blow flies etc. Thanks so much.

    Karen

    When it comes to the concentration of the solution you use with your fogger, I would stick with what the label recommends. Since a higher concentration can lead to problems like a clogged fogger or cause harm to you or your cows.
    A lot of fogging solutions that target mosquitoes also are meant for killing flies. But more specifically, I’d suggest you look into ExciteR.

Ryan Lee

Hi, I have just bought a thermal butane powered fogger for cinematography purposes – are there any non-toxic non dangerous solutions I can use that wont harm people or the environment and that will still produce a good amount of fog? I have read to use mineral oil but apparently that isn’t good either?

    Karen

    Not sure what you could use instead of a fogging liquid since I haven’t used a thermal fogger for cinematography purposes. But yes, I have read as well that using mineral oil isn’t the safest. Some people recommend using either Vegetable Glycerin or Propylene Glycol instead of mineral oil since these two substances are used in electronic cigarettes so that might be an option you could look into. Or if you do decide to use mineral oil then go for the food-grade one and only use this method to create fog outdoors.

    Doreen

    Can you use cedar oil in a thermal fogging machine

    InsectCop

    First, you should check if your thermal fogger is meant for oil-based solutions. If your fogger is compatible with oil-based products, there shouldn’t be a problem.

Ned

Dear Karen,
I am reaching you from Nigeria( a tropical country) I have a challenge controlling mosquitoes in my yard especially during the rainy season. I spray Pyrethin and pyrethroid based solution into mosquito breeding areas but after rainfall , mosquitoes come back , what is the best solution for combating mosquitoes in tropical areas with heavy rainfall.
Thank you,
Ned

    Karen

    Thanks for your comment, Ned. I’d suggest you look into reducing mosquito breeding by using larvacides in addition to the sprays you’re applying to your area. Things like mosquito dunks and bits placed in areas that tend to collect water during rainfall and therefore become breeding grounds for mosquitoes can significantly reduce the mosquito population in your area.

Donna

I am a small hobby breeder and I am reaching out to get advice on types of foggers as well as products to get rid of ringworm. Vet supply websites usually always recommend only one product (Oxcine w/ citric acid) and one or two types of foggers, mostly the “oxcine fogger” or a hurricaine fogger with no explanation as to why. I would like to know if I have options.
Thank you in advance

    InsectCop

    It would probably be a good idea to go with what pet supply companies suggest. Their knowledge is more focused on animals therefore they will have a wider knowledge of what will be healthier to your livestock.

Gus Ochoa

Hi. Need some advice on what kind of fogger you recommend for disinfecting bedrooms.

    Kristiana Kripena

    It will largely depend on what type of disinfectant you’re planning on using. The disinfectant solution should have information on which kind of fogger it should to be used with. But in general, you can use both thermal and ULV foggers for disinfecting purposes.

Dave

Hello, I’m hypersensitive to mold and purchased a house that sits on a cement so lower the chances of the house becoming moldy. The drain for the bath tube was never connected and for 16 years whenever someone took a shower the water would run into the dirt causing mold and contaminating the the insulation on the north side of my home. I’ve remediated using bleach but it only worked short term so now I’m using microban which seems to work better and last longer. Would it be more beneficial to use a cold fogger or one that uses heated coils. Thank you

    InsectCop

    We do not specialize in the mold. However, combined with the right solution, a ULV fogger should help you deal with the problem.

Chet Pitts

Hello,

I have a Golden Eagle Curtis Dyna Thermal Fogger and I would like to know what type of disinfectant solution I can put into it to clean indoors. Should I keep it or get rid of the thermal fogger and get a ULV Fogger. I want a fogger that is easiest for me to find solution for.

    Kristiana Kripena

    The Golden Eagle Curtis Dyna Thermal Fogger is a powerful machine that is meant for dispensing oil-based solutions, including oil-based disinfectants. However, it will definitely be easier to find disinfectants that can be used with a ULV fogger. So, my suggestion would be to not get rid of your thermal fogger since it can still be useful for other applications, and to invest in a ULV fogger which is also safer for indoor use in general.

Karen Fabien

I will like to purchase the best fogger to disinfect and clean commercial space of virus and bacteria. Can you recommend the most effective fogger. How often should a commercial space be fogged?

    Kristiana Kripena

    For indoors I’d recommend a ULV fogger. As for how often should a space be fogged, I don’t specialize in disinfectants so I’d recommend you check the label of the disinfectant and see if there aren’t any guidelines for how often it should be applied.

Ashish Jain

These days variety of thermal and ulv foggers are being used for disinfecting areas from covid 19 virus. Which of these would you suggest and why

    InsectCop

    From the two types, ULV foggers would be a better fit, as they use pressure instead of heat to create the mist, which makes is better when it comes to fire safety. Also, ULV foggers give you an option to adjust the droplet size, giving you more options for the usage (e.g. disinfection, mosquito control, mold control).

Nicola

Hi, would a ULV fogger cause smoke/alarms to go off? Thanks

    InsectCop

    Technically, it’s possible. This can happen with pretty much any type of spraying if you do it close enough. Avoid spraying directly on or too close to the device. You should be fine.

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