Indoor air quality surveys, swab-sampling programmes and quantification of fresh air assessments must be carried out before businesses reopen to ensure the premises mitigate risks of transmission of Covid-19, according to a testing and certification company.
The Health & Safety Executive has published the latest guidance highlighting the risks of coronavirus transmission in air conditioning and ventilation systems, as many businesses prepare to reopen following two months of national lockdown. The guidance advises businesses to check that they have adequate air conditioning and ventilation systems in place to ensure that all areas of their premises are adequately ventilated to limit transmission of Covid-19 aerosol particles.
Those in the hospitality industry, non-essential retail and a number of other commercial buildings having closed to the public throughout the national lockdown and as they once again are faced with the well-versed processes of reopening, Bureau Veritas states that clean air and circulation in indoor venues should be a key part of their strategy as the UK exits lockdown.
Joe Marais, engineering team leader for occupational hygiene at Bureau Veritas, said: “There are two ways a business can adequately ventilate their premises. The first is natural ventilation, such as opening doors and windows. However, a number of buildings also use mechanical ventilation, these are air-handling (AHUs) and air conditioning units that control temperature, humidity, air movement and cleanliness within a space.
“The vast majority of AHUs are capable of introducing fresh outside air, mixed with a proportion of recycled air back into occupied areas. The key issue that we have found is that the fresh air ratio setting on AHUs has been drastically turned down due to the need to recycle air for thermal comfort. The latest guidance from HSE is discouraging the use of 100 per cent recirculation system settings and is encouraging the supply of fresh outdoor air too.”
Although the most common manner of Covid-19 transmission is through large particles or ‘droplets’, which are let into the air through sneezing, coughing and breathing and eventually settle on a surface, there is evidence to suggest that the virus can be spread by smaller particles called aerosols, which can remain airborne for several hours. It is these particles that pose the risk when indoor air is recirculated through an AHU.
Marais added: “While we’re all aware of the danger of coronavirus transmission via droplets and are regimented in social distancing and hand sanitising to prevent the spread, it can’t be forgotten that the virus can also spread via airborne particles, and thus the onus is on businesses to ensure all procedures are met to mitigate these risks for employees, visitors and customers.
“This can best be done by carrying out indoor air quality surveys to ensure that each area of the premises is well-ventilated, looking at where natural ventilation can be incorporated, as well as swab testing samples to assess whether the air that is being recirculated is free from harmful pathogens, especially the Covid-19 virus.
“Experts from our occupational hygiene team recently completed an in-depth assessment of AHUs and indoor air quality for a leading supermarket chain. The results of these air monitoring assessments were considered alongside other control measures currently in place throughout all UK stores, including social distancing, masks and the provision of hand sanitiser. In addition, our team took swab samples at two specific locations in each store to determine the presence or absence of the SARS-CoV-2 coronavirus gene.
“The result was an independent risk assessment and verification, on which our client could make a more informed decision over the risk of air recirculation in sales areas during the Covid-19 pandemic, as well as a comprehensive report containing the results of independent assessments on all five AHU variants.”