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Covid-19 decontamination strategies

01 November 2021

John Holah discusses cleaning and disinfection programmes for routine applications and for Covid-19 decontamination in food production environments. 

In the UK approximately 400,000 people work in food manufacturing. As such, and while the incidence of Covid-19 in the general population remains high, it remains likely that identified Covid-19 cases will continue to be identified amongst the food processing sector workforce.  Indeed, multiple outbreaks of Covid-19 have occurred among workers on farms and in food processing facilities.

Following the presence of a known Covid-19 incident in an enclosed space, such as a food production area, decontamination is required before the space can be returned to routine operations. 

Many studies have been undertaken on the survival of coronaviruses in the air and on surfaces, with estimates of survival ranging from between 72 hours and 64 days on surfaces and up to 24 hours in the air, dependent on temperature, humidity and ventilation.

Time is the best control of coronavirus, allowing natural inactivation of the virus wherever it is in the enclosed space, but this is clearly impractical as there will be a need to continue routine activities taking place in the space as quickly as possible in the event that a member of the workforce tests positive.

Environmental surfaces can be quickly cleaned and disinfected using any disinfectant approved to EN 14476, the European Virucidal disinfectant test.  But what about the air?  Chemical fogging is an obvious choice as it uses the same disinfectant chemicals as for surfaces, it is easy to undertake using readily available application equipment and is already a traditional technique used across the food industry.  

Terminology
We must be conscious of terminology, however. Chemical fogging is an automated technique that applies large volumes of chemicals into the air via compressed air and should not be confused with the use of hand-held surface misters or ‘foggers’ which have become common during the Covid-19 pandemic for applying small quantities of disinfectants to low-level, room surfaces. Chemical fogging is undertaken after personnel have vacated the enclosed space and incorporates a settlement time following fogging to allow for the fogged droplets to settle out of the air or be diluted via ventilation. Following the settlement time, personnel can re-enter the workspace.

The bactericidal efficacy of fogging, and its use as a practical technique in the food industry, was established in 1998 via a Ministry of Agriculture Fisheries and Food funded LINK project undertaken at Campden BRI.  A 2-3 log reduction of airborne bacteria following fogging for 30-90 min was established, but viruses were not tested at the time the project was undertaken as they were not perceived to be an issue within the food industry.

The performance of chemical fogging for the control of viruses in the air was thus unproven.  Holchem, part of the Kersia Group, commissioned Campden BRI to look at viral survival in the air following fogging using typical non-oxidative (triamine) and oxidative (peracetic acid or PAA) Kersia disinfectants and using industry fogging equipment.  Trials were undertaken in a dedicated aerobiology testing facility using surrogate enveloped and non-enveloped viruses of a similar size and shape to target pathogens (e.g. coronaviruses and norovirus).

The triamine based product achieved a >4 log reduction of enveloped viruses following 30 minutes fogging and 1-hour settlement. The PAA based product achieved a >4 log reduction of enveloped and non-enveloped viruses following 30 minutes fogging and 1-hour settlement.  Chemical fogging within these parameters thus achieved a similar level of virus inactivation in the air (>4 log orders) as would be required to ‘pass’ EN14476 for surface adhered viruses.

Chemical fogging, using an appropriate disinfectant and disinfectant concentration, volume and contact time, can be used to decontaminate the air in an enclosed space in approximately 90 minutes. The speed of this technique therefore allows its consideration for both post-incident decontamination or routine decontamination of enclosed spaces more likely to have a Covid-19 incident because of high human use.”

John Holah is principle corporate scientist at Kersia.


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