During the COVID-19 pandemic, fogging became one of the most visible, and most debated, ways to disinfect buildings. Thermal foggers, ULV cold foggers and electrostatic sprayers were used everywhere from offices to stadiums. This guide summarizes what regulators and researchers have said about fogging against SARS-CoV-2, the virus that causes COVID-19, and how to use it responsibly today.
Short answer: fogging can help in specific situations, but only as a supplement to cleaning, only with products whose label allows that application method, and only when contact time and re-entry instructions are followed. It is not a substitute for cleaning, ventilation or targeted disinfection of high-touch surfaces.
What regulators said
U.S. Environmental Protection Agency (EPA)
EPA maintains List N, its list of disinfectants for use against SARS-CoV-2. EPA has stated that unless a product's label specifically includes directions for fogging, fumigation, wide-area or electrostatic spraying, it has not reviewed data on whether the product is safe and effective when applied that way, and it does not recommend using those methods with that product. In EPA's words, a disinfectant's safety and effectiveness "may change based on how you use it."
World Health Organization (WHO)
In May 2020, WHO advised against the routine spraying or fumigating of disinfectants on indoor surfaces, noting it may be ineffective outside the direct spray zone, and said that when disinfectants are used, they should be applied with a cloth or wipe soaked in disinfectant. WHO also advised against spraying outdoor spaces such as streets, and said people should never be sprayed with disinfectants.
U.S. Centers for Disease Control and Prevention (CDC)
In April 2021, CDC updated its guidance to note that the risk of getting COVID-19 from touching contaminated surfaces is generally considered low, and that routine cleaning is usually enough to reduce that risk. Disinfection is recommended when someone in the space has been sick with COVID-19 within the last 24 hours. Because the virus spreads mainly through the air, ventilation and other respiratory measures matter far more than surface treatments.
What the research shows
Controlled laboratory and field studies show that some disinfectants can inactivate coronaviruses when delivered as a fog, under the right conditions:
- Dry fogging, hypochlorous acid and hydrogen peroxide: a study published in PLOS ONE (2022) found that dry fogging hypochlorous acid and hydrogen peroxide solutions inactivated SARS-CoV-2 and influenza A virus in controlled tests.
- Dry fogging, peroxide-based disinfectants: research in Applied and Environmental Microbiology (2021) found that airborne dry fogging inactivated SARS-CoV-2, mycobacteria and bacterial spores, while noting limits of commercial spore test carriers.
- Thermal fogging in cold chains: research published in the Journal of Applied Microbiology (2022) reported that thermal fogging with a quaternary ammonium disinfectant (didecyl dimethyl ammonium bromide) combined with antifreeze effectively killed a coronavirus, an influenza virus and indicator bacteria in sub-zero cold-chain environments, where conventional wet disinfection is difficult.
- Hydrogen peroxide fogging systems have also been studied for whole-room disinfection in healthcare, education and other settings.
These results are encouraging, but they come from controlled conditions with specific products, concentrations, exposure times and room setups. Real-world results depend on the same factors, plus how clean the surfaces are before treatment.
Why fogging alone is not enough
- Soil blocks disinfectants. Dirt, grease and organic matter shield microorganisms, so surfaces must be cleaned first.
- Coverage is uneven. Fog settles more on horizontal, upward-facing surfaces than on the undersides and vertical surfaces people touch.
- Contact time matters. Surfaces must stay wet for the label's contact time; very fine droplets can evaporate before then.
- Safety risks. Airborne disinfectants can irritate eyes, skin and lungs, so treated areas must be vacated and ventilated per the label.
Which chemicals were used with each method
| Method | Chemistries studied or commonly used | What the evidence says |
|---|---|---|
| Thermal fogging | Quaternary ammonium compounds, such as didecyl dimethyl ammonium bromide (DDAB) | The only peer-reviewed coronavirus study we found for thermal fogging, in sub-zero cold-chain settings |
| ULV / dry fogging | Hydrogen peroxide, hydrogen peroxide with peracetic acid or silver, hypochlorous acid | Several controlled studies show inactivation of SARS-CoV-2 and other microbes |
| Electrostatic | Quats, accelerated hydrogen peroxide, hypochlorous acid, silver dihydrogen citrate | Efficacy depends on the product; EPA allows electrostatic directions on labels after review |
Quats tolerate the heat of a thermal fogger, which is why they appear in most thermal-fogging research. Hydrogen peroxide and hypochlorous acid break down with heat, so studies applied them as cold or dry fog.
Thermal fogging specifically
Thermal foggers create a dense, visible fog of very fine droplets using heat. That makes them very effective at penetrating large volumes, voids and outdoor areas, and they have long been used for mosquito and flying-insect control. For disinfection, they come with extra considerations:
- Only use products whose label specifically allows thermal fogging; not every disinfectant is suited to being heated.
- Thermal fogging involves heat and, in many units, combustion, so fire safety controls and trained operators are essential, and it is not appropriate for occupied spaces.
- Fogging solutions can leave residue, so it should not be used around exposed food, packaging or sensitive electronics.
- In the U.S., few EPA-registered disinfectants include thermal-fogging directions, and those that do are mostly for agricultural and animal premises. A product used in a study is not automatically legal to thermal-fog in a school, office or food plant.
- It is best suited to odor control, flying-insect and vector control, and large unoccupied industrial spaces where a label allows it, rather than routine indoor disinfection.
Responsible fogging: a checklist
- Clean surfaces before any fogging or spraying
- Use a product whose label allows the application method
- Match the technology to the space (electrostatic, ULV or thermal)
- Vacate the area and follow label re-entry and ventilation instructions
- Protect exposed food, packaging and sensitive equipment
- Wipe-disinfect high-touch surfaces directly
- Verify cleaning results, for example with ATP testing
- Document products, areas, dates and contact times
How Cavanto uses fogging
Electrostatic spraying is our primary disinfection method for surfaces, and ULV fogging systems are used for whole-room disinfection with products registered for that method. Thermal fogging is used for odor and flying-insect control where labels allow. Every application follows cleaning, uses label-approved products, and has documented contact times and re-entry intervals. For product examples by method, see Disinfectants by Application Method. See how the three technologies compare on our Technology & Verification page.
Sources
- EPA: Can I use fogging, fumigation, or electrostatic spraying or drones to help control COVID-19?
- PLOS ONE (2022): Inactivation of SARS-CoV-2 and influenza A virus by dry fogging hypochlorous acid solution and hydrogen peroxide solution
- Applied and Environmental Microbiology (2021): Airborne disinfection by dry fogging efficiently inactivates SARS-CoV-2, mycobacteria and bacterial spores
- Scientific Reports (2022): Biocidal efficacy of commercial disinfectants used during the SARS-CoV-2 pandemic
- Journal of Applied Microbiology (2022): Thermal fogging with disinfectants and antifreezes enables effective industrial disinfection in subzero cold-chain environment
- WHO guidance on spraying disinfectants, as reported May 2020
This guide is general information, not medical or regulatory advice. Guidance on COVID-19 has changed over time; always follow current EPA, CDC and local public health guidance and the product label.