Davie and McCulloch Ltd

In October, CIBSE  released version 4 of the COVID-19 Ventilation Guidance providing guidance on the set up and operation of ventilation systems. The UK Government and devolved administrations have produced guidance for employers, employees and the self-employed to help them understand how they can work safely during the pandemic. For the UK, the Health and Safety Executive (HSE) provides guidance on building safety in general and on air conditioning and ventilation in particular. Ventilation is a very important way of diluting any airborne pathogens and there is evidence showing that room occupants are more at risk of catching an illness in poorly ventilated rooms than in well-ventilated rooms.

Evidence suggests that in poorly ventilated indoor spaces airborne aerosols are a possible transmission route and the precautionary advice remains valid. Maintaining good levels of ventilation remains the key focus even in colder weather conditions, whilst minimising occupant discomfort due to draughts and lower indoor temperatures. As businesses continue to manage the return of staff to work premises and the continuing operation of buildings through the pandemic, a number of issues need to be considered for the safety of those entering buildings. Government guidelines should be followed.

To minimise the risks of far-field airborne aerosol transmission of SARS-CoV-2, the general advice is to increase the air supply and exhaust ventilation, supplying as much outside air as is reasonably possible. The underlying principle is to dilute and remove airborne pathogens as much as possible, exhausting them to the outside and reducing the chance that they can become deposited on surfaces or inhaled by room users. Recirculation or transfer of air from one room to another should be avoided unless this is the only way of providing adequate ventilation rates to all occupied rooms. In naturally ventilated buildings, strategies such as intermittent airing and partial window opening to complement background ventilation should be adopted.