The metaphor of using an entire arsenal of weapons to kill a fly illustrates the overuse of disinfectant dispensers in an emergency in attempts to minimize the risks of contamination and the spread of COVID-19.

Several manufacturers are taking advantage of the situation to praise the performance and benefits of their disinfectant dispensing devices: electrostatic sprayers or foggers. In return, some health experts are sounding the alarm and warning about the risks of disinfectants and the precautions to be taken during their application. The purpose of spraying is not to apply more disinfectant but rather to allow more effective application only if all conditions are favourable.

In some situations, using such devices involves more risks than benefits.

What is the difference between spraying, electrostatic spraying, fogging, and other methods? The effectiveness of each depends on the type of disinfectant, the pathogen targeted, the surfaces, the size of the interior space, the location of the device, pre-cleaning practices, organic load, air movement, relative humidity, disinfectant volume, and contact time.

Electrostatic vs. traditional spraying

The guns in electrostatic spray disinfection systems have a nozzle that contains an electrode to apply an electrical charge (positive or negative) to the disinfectant solution as it is expelled from the device. This charge increases the force of attraction and allows the droplets to completely coat and thus adhere to the entire surface to which they are directed, even if they are irregular in shape.

In comparison, traditional spraying is a form of passive application that is not recommended for combating COVID-19. With traditional systems, the expelled disinfectant droplets are not charged and their adhesion to surfaces is not guaranteed. Therefore, traditional spraying does not provide such uniform coverage of the surface and may even cause more harm. With the splash produced, germs can be carried away from the target area, potentially spreading and contaminating other surfaces.

Misting

Misting also consists of dispersing a disinfectant solution in the form of droplets. The droplets produced here are so fine that they stay suspended longer, allowing them to disperse in the air and provide uniform coverage when they land on a surface. But, due to the size of the particles, misting poses an even greater inhalation hazard to the worker or people in the environment.

The National Collaborating Centre for Environmental Health (CCNSE) recommends that only technicians or trained personnel should use misting or spraying devices. In addition, in the case of misting, protocols must be applied to ensure the safety of people, in particular:

• Evacuating the space to be treated.
• Sealing the doors, windows, and ventilation ducts of the room if people remain present elsewhere in the building.
• Condemning for a few hours the room that has been treated and, preferably, putting up a poster indicating the time when the treatment was done and the time when it will be possible to return to the room.
• Before entering, ventilating well to minimize negative allergic reactions.

The main advantages of electrostatic spraying

• The attraction charge provides optimum coverage of droplets on surfaces
• The marketing of electrostatic sprayers generally emphasizes the speed and the time savings provided by these devices. Studies show that the application speed can be up to 10 times faster than that of traditional tools (up to 14,000 square feet of office space per hour).
• The electrostatic sprayer also saves material by using 60% less chemical per square foot.

Risk of electrocution

Few manufacturers would put forward the risk of electrocution that can occur when handling electrostatic devices but, while the discharge is obviously low, the fact remains that it happens frequently. The step of grounding the device and following manufacturers’ recommendations is vital to prevent the user from receiving electric shocks.

Misleading advertising ads

Beware of false promises when it comes to sprayers. Here are some frequently encountered examples:

• Faster drying. In disinfection, we do not necessarily want a surface to dry quickly; we want to respect the contact time prescribed by the manufacturer.
• Disinfectant protection that lasts hours or days after a single application. This is not a benefit of the electrostatic sprayer, but rather of the disinfectant used. This statement is only true when using a chemical with persistent disinfectant properties, meaning it is able to provide protection for a certain period after application. Remember that disinfection is a temporary solution, while contamination is a permanent risk. Most of the time, as soon as a surface is touched or soiled, it is no longer disinfected!
• A disinfectant spray that kills COVID-19 and other germs quickly with extraordinarily little effort. It is not the device that kills pathogens, but the product used according to its properties (viral, bacterial, sporicidal …). Contact time varies depending on the product; some can be one minute, others 10 minutes. There may be little effort for the application of the disinfectant product but the first step of cleaning the surfaces with a detergent and a mechanical action to dislodge debris and microorganisms should not be neglected.

Health risks of overexposure to chemicals

It is recognized that spraying can cause allergic reactions of varying severity depending on the product that is sprayed and the sensitivity of each. Although symptoms are most felt after prolonged or repetitive exposure over time, experts agree that unnecessary overexposure to disinfectants should be avoided. Ontario Public Health notes that it is essential to follow the manufacturer’s instructions, in particular by wearing the appropriate PPE, and specifies that employees responsible for disinfection by electrostatic spray must ensure that all other people have left the premises.

It is important to remember that when an environment does not involve too many infectious risks for the health of users, there is no point in exposing them to chemicals dangerous to their health!

Product choice

Although Health Canada has a list of approved disinfectants for COVID-19, the products are not necessarily compatible with spraying or misting. It is the same scenario in the United States. Moreover, the Center for Disease Control does not recommend the use of an electrostatic sprayer or fogger for the application of a disinfectant solution, deeming the risks too high for users.

“The aerosolization risks of many ‘N-list’ disinfectants have not been investigated,” said Ian Cull, president of Indoor Sciences, an environmental consultancy. “And there are very few that are approved for aerosolizing, misting or fogging.” The EPA is continuing its research to find out whether sprayers and misters are effective against COVID-19.

The compatibility of the disinfectant solutions with the target surface, the infectious agent in question, and the environment must be considered. And, above all, you cannot disinfect without first cleaning. It is true that spraying saves time, but it does not eliminate the step of cleaning surfaces which must always be done beforehand to remove dirt and grime.

Spray recommendations:

• Train personnel in the use of the device and aware of the risks associated with operation.
• Develop a standardized process as clear and streamlined as possible so that it can be easily reproduced and adapted by staff for safe and compliant use.
• Always wear gloves and eye protection when spraying chemicals, wear long clothing to cover the skin and look into antistatic gloves to avoid electric shock.
• Never spray when people are in the room, especially children, who are more sensitive to the negative effects of chemicals than adults. Indeed, children must eat, drink, and breathe more per pound of body weight than adults due to their growth and development. Children are also less aware of the dangers and ways to avoid them, making them more vulnerable.
• Since electrostatic spray systems occasionally produce sparks, special attention should be paid to nearby sources of flammable gases, liquids, and dust. Avoid turning the sprayer into a flamethrower!
• Do not adapt a paint or fertilizer sprayer to spray disinfectant. Any device must be used in accordance with the manufacturer’s recommendations.
• Due to the increased risk of inhalation, a product in its concentrated form should never be sprayed. Dilution may differ depending on the method of application. The dilution recommendations must be followed to the letter and ensure the compatibility of the product with the device.
• Get advice! Consult professionals for any questions concerning the validation of the disinfection method, the choice of device, the choice of product, or application frequencies.

Derek Oliveira is a Senior Director for Gestion HB, a Canadian consulting firm that guides, supports, and advises its clients on ways to optimize the operational performance of their organizations in terms of building hygiene and sanitation.