3. How to improve ventilation

Practical ways to improve your ventilation include:

  • increasing natural ventilation by opening doors, windows and vents
  • ensuring that mechanical systems which recirculate air, including air-conditioning systems, have been designed with fresh air inlets and that they are kept open to avoid the air becoming unhealthy

You may need a combination of natural and mechanical ventilation.

How to improve natural ventilation

You can improve natural ventilation by fully or partly opening windows, air vents and doors. But do not prop fire doors open.

You should be able to open any windows and keep vents or trickle vents open that let in fresh air. If any windows have been painted shut, they should be reopened. If they cannot be opened, ventilation in that area will be less effective.

Airing rooms

If ventilation is poor, airing rooms can improve it as a temporary measure while awaiting longer-term changes. Opening all the doors and windows as fully as possible maximises ventilation in a room.

If it's too cold for the people in the room you can do this when they leave for a break. Even 10 minutes an hour can help increase the amount of fresh air, depending on the size of the room.

How to improve mechanical ventilation

Mechanical ventilation brings fresh air into a building from outside using ducts and fans. Providing it is working correctly, it has the advantage of providing fresh air consistently. However, it may be more costly, requires energy to operate the system and needs to be properly maintained.

It’s important to make sure that clean outdoor air is actually supplied, rather than assuming outdoor air is clean. If you expect the air coming in to be heavily contaminated with particulates such as heavy traffic or smoke, then it should be filtered.

You should speak to the people who manage the day-to-day operations of your workplace's mechanical ventilation systems to:

  • understand how they operate
  • make sure they're supplying fresh air into an area and how much
  • make sure they're maintained in line with manufacturers' instructions

You may need a ventilation engineer to check your system is providing adequate ventilation.

Use of recirculated air

Air to be recirculated should be adequately filtered to remove particulates and should have fresh air added to it before being reintroduced into the workplace.

HSE’s Approved Code of Practice states 'In the case of mechanical ventilation systems which recirculate air, including air-conditioning systems, recirculated air should be adequately filtered to remove impurities. To avoid air becoming unhealthy, purified air should have some fresh air added to it before being recirculated. Systems should therefore be designed with fresh-air inlets, which should be kept open.'

If your ventilation is still poor

If your ventilation is still inadequate, for example if CO2 readings remain above recommended levels or the room continues to feel stuffy, you could consider:

  • changing how workspaces are used, for example restricting the length of time people spend in them or the number of people using them at a single time
  • installing a mechanical ventilation system (upon advice from a ventilation engineer), if there is no mechanical ventilation already or if the existing system does not provide fresh or purified air

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