The meeting room feels stale by lunchtime. Staff open a window, someone closes it because of a draught, and the problem returns next week. A workplace ventilation assessment should replace this cycle with a clear understanding of how fresh air enters each occupied space, whether it is adequate for its use and who will fix any shortfall. A comfortable temperature alone does not answer those questions.
Start with the fresh-air duty
HSE explains that employers must provide adequate ventilation in enclosed workplaces. Regulation 6 of the Workplace (Health, Safety and Welfare) Regulations requires sufficient fresh or purified air. Fresh outdoor air can arrive through windows and vents, a mechanical system or a combination. The relevant question is what actually reaches the people using the room.
This guide concerns general workplace ventilation. Dust, fumes and other process contaminants need their own assessment and controls; opening a window is not a substitute for suitable source capture. Equally, a desk fan moving existing room air does not itself introduce fresh air.
Keep the assessment proportionate. A small office with straightforward opening windows may need a documented walk-through and practical checks. A mechanically ventilated building with unknown supply rates or persistent problems may need a competent ventilation engineer.
Assess rooms as people actually use them
Use a floor plan or room list. Include offices, meeting rooms, break rooms, changing areas and other enclosed spaces where people spend time. Record normal and peak occupancy, typical duration of use and activity. A room that worked well for two desks may perform differently after six people move in.
Look for spaces with no obvious fresh-air supply, stuffiness, persistent unpleasant smells or ventilation that users cannot operate. Ask staff when problems occur. The early shift, busy lunchtime or weekly team meeting can reveal conditions that a quiet afternoon inspection misses.
Then identify the ventilation route. Which windows open safely? Are vents obstructed? Is there an extract fan, and where does replacement air enter? For mechanical systems, ask the person maintaining them whether they supply outdoor air, recirculate indoor air or do both. Cooling equipment being switched on is not proof of a fresh-air supply.
Use CO2 readings as supporting evidence
HSE recommends non-dispersive infrared CO2 monitors for this purpose. Place a monitor around head height, more than 50 centimetres from people and away from windows, doors and supply vents. Follow calibration instructions and take repeated readings during occupied periods, recording occupancy and ventilation conditions alongside them.
HSE says readings consistently above 1,500 parts per million in an occupied room indicate poor ventilation and require action. This is an indicator, not a legal exposure limit or a declaration that every reading below it is safe. A single reading in an empty room tells you little about a busy meeting later.
CO2 is less useful where occupancy is low or variable, air does not mix well or another process produces the gas. It does not measure every pollutant or the effectiveness of an air cleaner. In complex spaces, obtain competent advice rather than forcing a room onto a simple traffic-light chart.
A practical example: the meeting room that changed use
Consider a Gateshead business that has converted a small interview room into a daily training room. Its assessment still describes occasional two-person use. The new sessions involve eight people for several hours, and a display board now covers a wall vent. Staff disagree about whether the air conditioning solves the problem.
The useful response is to record the changed use, remove the obstruction safely, establish what the equipment supplies and check conditions during a representative session. While a lasting solution is arranged, the business can move sessions to a suitable room or reduce occupancy and duration. The choice should follow the assessment, rather than an arbitrary building-wide headcount rule.
Assign an owner and completion date. Once changes are made, repeat the checks during comparable use and ask the occupants whether the practical problem persists. Buying a monitor without assigning responsibility for responding to its readings leaves the original management gap in place.
Turn room concerns into an action plan.
HR + SAFETY's health and safety support can help structure the assessment, record practical controls and identify when specialist ventilation advice is needed.
Discuss a ventilation concernImprove the supply without creating a new problem
Start with the existing provision. Restore usable windows and vents, clear obstructions and ensure mechanical ventilation operates when rooms are occupied. If fresh-air delivery remains unclear, have a competent person inspect the system and confirm appropriate settings. Recirculated air, even when filtered, needs a suitable fresh-air supply alongside it.
Do not prop open fire doors to solve ventilation problems. Opening windows must also account for security, falls, outdoor pollution and other site conditions. Temporary airing can help while an improvement is arranged, but it should not become an unexamined substitute for adequate provision during use.
In colder North East weather, consider higher-level openings, smaller openings across the space or adjusting workstation positions to reduce uncomfortable draughts. Explain the agreed arrangement to staff so the next person does not unknowingly undo it. Temperature and ventilation need to be managed together.
Connect maintenance and workplace decisions
Give facilities staff or the maintenance contractor a clear description of the problem: which room, when, occupancy, existing settings and any measurements. Ask for an explanation of the remedy and how continuing performance will be checked. A service visit should produce enough information for the business to know what has been repaired or adjusted.
Keep ventilation information available when layouts or room uses change. Partitioning an office, adding desks or turning a store into an occupied workspace can alter the assumptions behind the original arrangement. Include a ventilation check in the change process, alongside access, welfare and fire precautions.
Consult workers about the result, including anyone whose health or working arrangements require individual consideration. Do not dismiss repeated concerns simply because the central system has received a routine service. The occupied room is where the arrangement needs to work.
A room-by-room ventilation checklist
- Identify every occupied enclosed space and its busiest realistic use.
- Record how fresh air enters and how indoor air leaves.
- Check obstructions, controls and whether users understand the arrangement.
- Use suitable CO2 monitoring where it can provide meaningful evidence.
- Record problems, interim controls, responsible people and deadlines.
- Obtain competent engineering advice where capacity or performance is uncertain.
- Check improvement during normal use and retain maintenance information.
- Revisit the assessment when occupancy, layout or working patterns change.
Treat fresh air as a workplace provision that needs ownership. Establish how it reaches each room, investigate problems during actual use and confirm that improvements work. A monitor can inform that decision; it cannot make it for you.
This guide provides general information for UK employers. It is not legal advice and should not replace advice based on the facts of a specific matter.