Beta This is a new way of showing guidance - your feedback will help us improve it.

Disinfecting using fog, mist and other systems during the coronavirus (COVID-19) pandemic

This page has advice on systems used to disinfect premises during the pandemic. It explains the legal requirements and provides the latest information, including joint advice from public health bodies on risks to health that can be created by using walk-through spraying or misting systems.

Risks from walk-through disinfecting systems
Disinfecting premises using fog, mist or UV treatment
The law on disinfectants
Only use HSE-authorised products in the UK
Supply and manufacture of disinfectants

Risks from walk-through disinfecting systems

The Health and Safety Executive (HSE) and public health bodies in England, Wales and Scotland have agreed the following joint advice for dutyholders considering using walk-through spraying or misting disinfecting systems to reduce transmission of coronavirus (COVID-19).  

These systems use a tunnel, portal, booth or other equipment and have been designed to apply disinfectant to people as they pass through.

Spraying people with disinfectants is not recommended under any circumstances (including in a tunnel, cabinet, or chamber). The World Health Organisation has also confirmed that it could be harmful and does not reduce the spread of the virus. This is because transmission is usually through droplets or contact, so the effectiveness of these systems is likely to be minimal.

Even where a person who is infected with COVID-19 has passed through a disinfection system/device, as soon as they start speaking, coughing or sneezing they can still spread the virus.

Disinfectants used in this way are potentially harmful and can cause health effects including respiratory and eye irritation. For further information see the paper published by the government's Scientific Advisory Group for Emergencies (SAGE) on whole-body walk-through systems.

You should use standard control measures to manage the risk of COVID-19 transmission including social distancing, frequent cleaning, adequate ventilation and regular handwashing. Any relaxation of these proven, effective control measures can increase the risk of viral transmission.

Disinfecting premises using fog, mist or UV treatment

Fog, mist, vapour or UV (ultraviolet) treatments may be suitable options to help control the spread of coronavirus and disinfecting a larger space or room. Any use of these treatments for these purposes should form part of your COVID-19 risk assessment. Users must be competent and properly trained.

If you choose to use fog, mist, vapour or UV treatments as a way of disinfecting surfaces, discuss your requirements with your manufacturers/suppliers (this may include fumigators), to help you decide if a product/system meets your needs. The treatment you use will depend on:

  • the size of the area to be treated, its shape and how easily it can be sealed off while delivering an airborne product
  • whether there are hard or soft surfaces – soft furnishings may act as a 'sink' for the airborne chemicals and emit them for a period of time after treatment (remove items such as sofas before treatment)
  • the type of business you have – some areas may be better suited to UV surface treatments than airborne chemicals or vice-versa, for example, if rooms cannot be adequately sealed to contain airborne chemicals

Disinfectants applied as a fog, mist or vapour may reach harmful levels during delivery and UV systems may cause eye/skin damage if people enter an area undergoing treatment.

People should not enter rooms being treated by UV or disinfectants applied as fog, mist or vapour.  Discuss with suppliers what safety features they can provide to prevent inadvertent access to a room during treatment, for example hazard-monitoring sensors.

Locking rooms during the treatment will help to contain the emissions but other measures such as taping of doorway gaps or plastic screening off of some areas of the room may also be required.  Good ventilation will also help clear the disinfectant after the treatment if this can be controlled from outside of the room.

Any equipment used to deliver the disinfectant by these means must comply with the relevant UK law – the Supply of Machinery (Safety) Regulations.

Fog, mist, vapour method

If using fog, mist or vapour, you should ensure the correct concentration of the active chemical is used to achieve disinfection. However, be careful not to apply too much so that it leaves a wet surface or residue, which may present a hazard to anyone entering the room after the treatment is completed.

Methods used include disinfectant or generating reactive gases, for example ozone from air or bottled oxygen. Hydrogen peroxide may be used as a cold mist or as a thermally generated vapour.

Airborne disinfection does not remove the need for surface cleaning and surfaces that are dirty can reduce the effectiveness of disinfectant applied by airborne dispersion.

Disinfectants dispersed by fog, mist, or vapour may not result in even application to all surfaces.Hidden or 'shadowed' surfaces, or the surface underneath objects, may not be disinfected. The use of these methods in rooms of complex design with multiple surfaces may not be suitable.

Seek advice from your supplier on what treatment is appropriate for the environment you are disinfecting.

UV method

Compared to disinfectants applied as a fog, mist or vapour, UV treatment of surface normally leaves no chemical residue behind. However, UV may present a risk for injury to unprotected skin and eyes if operators do not take necessary precautions.

In very small spaces, such as small sanitary areas, some UV treatments may not be suitable if the units need to be placed at a minimum distance from walls etc to be deployed safely.

Some sources of UV light can only destroy micro-organisms where the light can fall on surfaces for a sufficient time – you should seek advice from your supplier.

Sealing off rooms

For fog, mist or vapour treatments, gaps in doors or windows can allow leakage of hazardous chemicals back into the building beyond the area being treated. You should therefore seal potential leak points to minimise the risk of exposure to people. Equipment suppliers can provide advice on this procedure.

Chemical sensors placed inside the treated room, or hand-held sensors, can be used to monitor the concentrations of chemicals to indicate it is safe for operators to enter the room.

Rooms that are difficult to seal may not be suitable for delivering airborne chemicals and this must be decided as part of a risk assessment, before starting any treatment.

Large outdoor spaces

Large-scale spraying or disinfecting in outdoor spaces, such as streets or open marketplaces, is not recommended for COVID-19 or other pathogens. This is because you cannot control dispersion of the chemical hazards and possible unintended exposure to people.

Streets and pavements are not considered as routes of infection for COVID-19. Spraying disinfectants, even outdoors, can be dangerous to people's health and cause eye, respiratory or skin irritation or damage.

The law on disinfectants

Ensure that you follow the manufacturer's instructions to ensure you are using the product safely and effectively.

Where units/machines are used in a workplace, under the Control of Substances Hazardous to Health Regulations (COSHH) employers must ensure substances which may be harmful to people's health from their work activities are identified and assessed, and processes are put in place to eliminate or control risks.

COSHH also requires employers to provide information, instruction and training for all their employees who use hazardous substances such as disinfectants in their work, including the appropriate precautions and actions employees must take to safeguard both themselves and others in the workplace.

Disinfectants used in this way to control/kill harmful organisms such as bacteria and viruses are biocides and need to comply with the Biocidal Products Regulation concerning the supply and use of biocidal products.

Only use HSE-authorised products in the UK

Only HSE can authorise biocides under the Biocidal Products Regulation in the UK. Any statement that the biocide is endorsed by another regulatory body or organisation is not relevant and does not override the requirements of the Regulation in the UK.

The Regulation also prohibits any advertising of a biocidal product which is misleading in respect of the risks from the product to human health, animal health or the environment or its efficacy.

Advertising for a biocidal product should not mention 'low-risk biocidal product', 'non-toxic', 'harmless', 'natural', 'environmentally friendly', 'animal friendly' or any similar indication.

Even where products are not specifically labelled as hazardous, dispersing them in mist, fogs or vapour increases the risk that they can enter the lung. In some individuals with respiratory conditions, such as asthma, this may provoke their symptoms.

Supply and manufacture of disinfectants

The disinfectant applied as a fog, mist or vapour treatment must comply with the Biocidal Products Regulation (BPR). This includes the generation of ozone or free radicals. Please note the use of UV to disinfect is not covered by the BPR.

Under the BPR, it is the disinfectant, or the chemical used to generate the disinfectant, added to the machine, that is the biocidal product. Please note that the machine itself is not covered by the BPR.

Suppliers of fog, mist or vapour units/machines should ensure that any disinfectant products they supply or recommend using with the unit/machine comply with the BPR.

There is separate guidance on the regulatory requirements for surface disinfectants manufactured and supplied during the pandemic, which applies to disinfectant products applied via fog, mist, vapour units and other machines.

Manufacturers of disinfectant products are responsible for ensuring that their products are suitably effective, including meeting any necessary testing standards. They are also responsible for providing information and instructions for the user on the product label.

Find out more

The Scientific Advisory Group for Emergencies (SAGE) have produced a paper on air cleaning devices and whole-body walk-through systems.

There is general coronavirus information for people and businesses in Scotland and Wales.

Page last reviewed: 03 March 2021

Next review due: 31 March 2021

2021-03-08