Update on Ventilation and air conditioning for safer work spaces

22-March-2021 10:21
in General
by Admin

It’s been a while since we posted our first blog on VENTILATION AND AC SYSTEMS AND THEIR EFFECT ON THE TRANSMISSION OF VIRUS PARTICLES back in June 2020. Since then, experts and the public alike have learnt so much more about the coronavirus and its transmission in open and closed spaces. With this new knowledge, the HSE has updated and expanded its advice to help employers provide adequate ventilation in their workplaces during the pandemic.


Whilst your building should have the legal requirements for ventilation, there may be some areas that now pose a higher risk due to aerosol transmission. To prioritise high risk areas, first assess parts of your workplace that are usually occupied and are poorly ventilated.


So, where do you start with identifying poorly ventilated areas in your workplace?

The HSE guidelines suggests these simple ways of assessing your workplace ventilation;

  • Look for areas where people work and there is no mechanical ventilation or natural ventilation such as open windows, doors or vents etc.
  • Check that mechanical systems provide outdoor air, temperature control or both. If a system only recirculates air and has no outdoor air supply, the area is likely to be poorly ventilated.
  • Identify areas that feel stuffy or smell bad.
  • You may wish to use carbon dioxide (CO2) monitors. Checking CO2 levels will help you decide if ventilation is poor. The monitors are less effective in areas used by few people .

Once the poorly ventilated areas have identified you must then consider which type of is ventilation needed . When deciding, you must consider factors including;


  • How many people use or occupy the area?
  • How much time do people spend in the area?
  • The size of the area
  • What tasks or activities take place in the area?
  • Are there any features in the workplace that affect ventilation?
  • Does your workplace use local exhaust ventilation?
  • Is there a complex ventilation system?

Although the law pre Pandemic required employers to make sure there’s an adequate supply of fresh air (ventilation) in enclosed areas of the workplace. The HSE is urging employers to to look further into how they can maximise the fresh air in shared work spaces. Let’s take a look at how you can identify and implement these ventilation methods.

natural ventilation

This relies on passive air flow through windows, doors and air vents that can be fully or partially opened. You can optimise this method of ventilation by;

  • Keep windows or doors at least partially open when people are using or occupying a naturally ventilated area.
  • Identify poorly ventilated areas and decide if that area should continue to be used until improvements are made.
  • Frequently Air your work space by fully opening doors and windows. This may be more appropriate when the space is unoccupied.
  • Ensure you communicate the importance of natural ventilation to all staff members so they can understand the processes and play their part in reducing the risk.

mechanical ventilation

This form of ventilation relies on using fans and ducts to bring in fresh air from outside or a combination of natural and mechanical ventilation. Here’s how you can Improve mechanical ventilation and AC systems in your workplace;

  • Speak to your property manager/building maintenance provider to understand how your systems work, if they are using an appropriate fresh air source and if they are being serviced as per manufacturer's instructions.
  • Maximise fresh air and minimise recirculation understanding how much fresh air your ventilation system draws in and if this provides adequate ventilation. You may need to increase the rate or supplement with natural ventilation where possible.

Granted that adequate ventalation is key to reducing the risk of aerosol transmission in a work place, there are other best practices you can implement to further efforts such as making sure infected workers (or any visitors with coronavirus symptoms) do not come into the workplace, limiting the number of people in an area and encouraging workers to spend less time in occupied areas.

If you need help to understand what you should do with ventilation and AC systems in this pandemic, please feel free to call Karsons Consulting today 020 3282 7605 or

The information in this blog has been sourced from the official HSE Ventilation and air conditioning during the coronavirus (COVID-19) pandemic guide. Visit to read more.