Mist management
Steve Teasdale, Co-Founder and Chief Scientific Advisor at InnuScience Group, explains why we need to see through the clouded thinking about fogging.
We’ve all seen in the news the videos and images of people and trucks travelling down city streets fogging disinfectants on sidewalks. It’s a sight many of us have never seen but in the climate of this pandemic, fogging is seen as a way to save time in disinfection, and is perceived as
being more effective than a regular disinfection. This is not necessarily the case though.
Options for disinfectant application
The old ways are the simplest. Take a cloth (microfibre is better as it helps remove surface-borne particles more effectively) and soak it with a disinfectant. It’s probably the most effective way to disinfect surfaces. Many people work using a trigger spray, spraying the disinfectant on the surface, and then applying the mechanical action. When spraying with a simple trigger spray the downside is that it’s very localised and there’s a large area that remains outside the spray pattern, as if in a ‘shadow effect’.
This is where electrostatic sprayers come into play. These systems spray small droplets which are electrically charged so they are attracted to surfaces. This reduces the ‘shadow effect’ allowing the droplets to surround or wrap round the object or
surface.It’s possible to
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combine fogging with electrostatic fogging, which isn’t that common but does exist. Fogging is also called nebulising, atomising, or misting. When fogging a disinfectant in a closed space it is mostly referenced as ‘all room disinfection’ or ‘environmental disinfection’, but also ‘environmental fogging’ or ‘no contact no touch disinfection’. When used in the healthcare sector it is known as ‘terminal’ or ‘final disinfection’.
Whichever term is used, it refers to an application that saturates the air of a space or room with a disinfectant using fogging equipment and a disinfectant chemical, typically a quaternary ammonia or super oxidants like hydrogen peroxide vapour (HPV). Chlorine dioxide can also be used to fog or ozone (which is not really used through a fogging system), but still saturates the air of a closed space with ozone, so it's considered to be all room disinfection. Finally, there are UV systems to provide all room disinfection.
The question must be whether large-scale fogging, as is becoming common, makes sense and whether we should be concerned.
Chemical and HPV fogging
The droplets generated by the fogging systems are extremely fine, but still behave like solid particles, meaning they fall out of the air. So even though you’re saturating the air of a closed space, and while horizontal surfaces will be well covered, vertical surfaces will need more contact time. In this scenario, electrostatic fogging would be more effective. Most use regular fogging systems simply extend the fogging time. This becomes critical when you combine the fact that the airborne disinfectant falls rapidly to a
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