surface, risking a repeat of the ‘shadow effect’ mentioned earlier, leaving some parts of a surface untreated or insufficiently covered by the disinfectant being applied.
Fogging systems range from low pressure to high pressure. Low pressure systems are essentially fed using tap water pressure along with a pump that generates a little mist. In the professional sector it’s more common to see the high pressure systems which can go up to 1500psi or 100 bars. These high-pressure systems are more effective, but they’re naturally more expensive, and the droplet size they generate is in the range of microns. This allows the droplets to stay airborne longer, providing improved saturation of the air in the space to be treated.
There are also fogging systems which are fixed and/or mobile. Recent media coverage commonly shows mobile units, while fixed systems are typically found in food processing plants where the need for microorganism counts as close to zero as possible is key to the operation. These are prevalent in areas such as the goods reception areas where trucks, pallets and people are present. A safe transition area between the highly contaminated reception area and food processing is required.
The fogging
that the dosage per cubic metre is accurate and ensures effective disinfection. For optimal disinfection to occur, all the surfaces should first be thoroughly cleaned, and high touch surfaces should be disinfected as usual.
Chemical fogging using, for example, a quaternary ammonia, will have a typical fogging time anywhere between 15 to 30 minutes; to this add the dwell time of 45 to 60 minutes. Using hydrogen peroxide as a disinfectant extends the time. Ironically, using hydrogen peroxide as a surface disinfectant in the traditional way using a microfibre cloth, has a very rapid contact time, counted in seconds compared to a QUAT, which can need as much as 10 minutes. When used in fogging machines, it’s the complete opposite with teams typically fogging for two to four hours.
“Properly following correct
fogging procedure using proven and suitable products, with appropriate equipment,
process Recently there’s been a significant increase in the numbers of people who have never fogged before turning to the system. During the pandemic they’ve sought solutions to meet critical needs in the most cost- efficient and quickest route. However, to properly follow a correct fogging procedure using proven and suitable products, with appropriate fogging equipment, is not always the quickest or cheapest option.
is not always the quickest or
cheapest option.”
For fogging to work effectively the person or service provider must make proper calculations. For example, a mobile fogging system will be typically able to treat a 200 cubic metre closed space, so it is essential to know the volumetric size of the room to be treated, and then calculate the right concentration of the chosen disinfectant, so
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Something that’s especially important, but is regularly overlooked, is a room’s humidity level. To be effective at fogging using hydrogen peroxide, the humidity level must be below 40%. If it's above 40%, then the efficacy will rapidly decrease. Many people do not consider room humidity which is just one example of where the unscrupulous service provider may fall down.
What disinfectants
can be fogged? Basically, any water-based disinfectant in any fogging system will work; there is no restriction in terms of the functionality, and it’s unlikely to damage the machine. But not all disinfectants should be used as they have different consequences when they're used with fogging systems.
In terms of regulation, disinfectants need to be registered in most countries as proof of efficacy in activity, but
the fogging systems used to apply these disinfectants also have to be approved in some countries and should be submitted for proper registration in combination with a specific disinfectant. The reality is, many companies do not register their mix of fogging machine and disinfectant, even less so in circumstances such as the current pandemic where everything is moving fast.
Many regulatory bodies do not support nor recommend chemical fogging, excluding hydrogen peroxide and chlorine dioxide. Fogging using quaternary ammonia or
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