This guidance is based on the latest information and may be updated as and when new information becomes available.
AHU’s and Central Ventilation with recirculation functionality
Employers must, by law, ensure an adequate supply of fresh air in the workplace and this has not changed.
Good ventilation can help reduce the risk of spreading coronavirus, so focus on improving general ventilation, preferably through fresh air or mechanical systems.
Where possible, consider ways to maintain and increase the supply of fresh air, for example, by opening windows and doors (unless fire doors).
Also consider if you can improve the circulation of outside air and prevent pockets of stagnant air in occupied spaces. You can do this by using ceiling fans or desk fans for example, provided good ventilation is maintained.
The risk of transmission through the use of ceiling and desk fans is extremely low providing there is good ventilation in the area it is being used, preferably provided by fresh air. (HSE)
It is recommended to avoid central recirculation during SARS-CoV-2 episodes to prevent the risk of airborne transmission and recirculation of airborne viral particles in the building. The advice is to close recirculation dampers via the Building Management
System or manually.
Bypassing the recirculation section may impact the building cooling or heating capacity; this has to be accepted because it is more important to seek to reduce contamination and protect public health than to guarantee thermal comfort. This may require education
for building occupants and a relaxing of dress codes.
Some air handling units and recirculation sections may be equipped with return air filters. This should not be a reason to keep recirculation dampers open as these filters do not normally filter out particles with viruses. (CIBSE)
The risk of air conditioning spreading coronavirus (COVID-19) in the workplace is extremely low as long as there is an adequate supply of fresh air and ventilation.
You can continue using most types of air conditioning system as normal. But, if you use a centralised ventilations system that removes and circulates air to different rooms it is recommended that you turn off recirculation and use a fresh air supply.
You do not need to adjust air conditioning systems that mix some of the extracted air with fresh air and return it to the room as this increases the fresh air ventilation rate. Also, you do not need to adjust systems in individual rooms or portable units
as these operate on 100% recirculation. You should still however maintain a good supply of fresh air ventilation in the room.
If you’re unsure, ask the advice of your heating ventilation and air conditioning (HVAC) engineer or adviser. (HSE)
For further information and advice, contact Danny.Keenan@bradford.gov.uk or Tel 01274 437489 Mob 07582 101918