Publication - Advice and guidance

Coronavirus (COVID-19): ventilation guidance - November 2020

Guidance to support the mixing of individuals safely in indoor domestic and commercial properties.

Coronavirus (COVID-19): ventilation guidance - November 2020
Supporting staff

Supporting staff to understand the importance of ventilation

Improving the dilution of aerosols is not just about better levels of fresh air entering a building, it’s about how it then travels and eventually leaves the building. In its simplest form, the diagram below shows air coming in and then rising based on natural convection as it warms up before exiting through designed or accidental exit points. This simplistic picture should help in understanding the basic concept that is the focus of this guidance.

The effectiveness of ventilation in many environments is strongly influenced by user behaviour and an understanding of what measures are introduced. This could be as straightforward as individuals opening windows, which others then close, increasing the number of touchpoints (which should be cleaned regularly to reduce the risk of transmission) within an office environment and potentially leading to less physical distancing.

Clear instructions to building users is required on how ventilation systems should be used, particularly as we move into winter. There is an increased risk of user interference with systems, which could affect the measures taken to improve ventilation in buildings. This can be complex due to the variety of ventilation systems available, and as such employers should consult manufacturers’ instructions and with engineers with expertise in such equipment, as required.

Raising awareness of the potential for airborne transmission and the importance of ventilation will be key to ensuring that guidance is followed. The focus in the shorter term is to look at supporting businesses to improve the standard of ventilation in premises, with a clear steer that occupancy should remain reduced and that working at home should be implemented/continued, where this is possible.

Thermal comfort

Environmental factors (such as humidity and sources of heat in the workplace) combine with personal factors (such as the clothing a worker is wearing and how physically demanding their work is) to influence what is known as thermal comfort.

Individual personal preference makes it difficult to specify a thermal environment which satisfies everyone. For workplaces where the activity is mainly sedentary, for example offices, the temperature should normally be at least 16 °C. If work involves physical effort it should be at least 13 °C (unless other laws require lower temperatures). In practice, offices are typically set to 21 °C.

When altering the ventilation of premises, employers may also wish to consider relaxation of uniform/dress code requirements as we move into the winter months, as rooms are likely to have increased ventilation during these months to prevent the spread of the virus. This is likely to affect thermal comfort in some situations.