Does your office air con help with hayfever, or make it worse?

For those responsible for workplace health or facilities, it's not typically a problem that feels feasible (or within their powers) to fix - however that may not be entirely true.

Keeping pollen out

The most obvious thing an air conditioning system does during pollen season is justify keeping the windows shut. That sounds trivial, until you consider that pollen counts peak in the early morning and late afternoon - the exact windows when staff are arriving, leaving, and when meeting rooms fill up with people who've just come in from outside.

A sealed, air-conditioned office gradually clears the air as it recirculates through the unit's filters. Over a full working day, that difference is noticeable for anyone with moderate to severe symptoms. Staff who'd otherwise be reaching for antihistamines every few hours, or working from home to avoid the potential spike in symptoms, may function better.

It's also worth identifying this within an employer’s legal obligations. The Workplace (Health, Safety and Welfare) Regulations 1992 require employers to maintain a working environment that is, so far as is reasonably practicable, safe and without risks to health. Hayfever rarely features in risk assessments, but for employees whose symptoms are severe enough to affect their capacity to work safely - operating machinery, driving, working at height - airborne allergen exposure is a legitimate consideration, not just a comfort issue.

Humidity and the mould problem

Many commercial AC units can run in dehumidifier mode, and this is where things get relevant beyond the summer months. Mould spores are a year-round allergen, and UK office buildings - particularly older stock, basements, or poorly ventilated areas - can sustain the damp conditions mould needs to spread. Facilities teams often address visible mould reactively, but maintaining indoor humidity between 40 and 60 per cent reduces the underlying conditions before growth becomes visible.

Staff with asthma tend to be more affected by mould spores than pollen, so a system that runs dehumidification through autumn and winter is doing something useful long after hayfever season ends. If your site has recurring respiratory complaints that don't follow the seasonal pattern, humidity levels are worth checking before assuming the cause is something else.

When the system makes things worse

A poorly maintained AC unit can actively worsen air quality. Filters that haven't been cleaned accumulate pollen, dust, mould spores and particles brought in on clothing - then push them back out across the office when the unit runs. If people in a particular area consistently feel worse when the air conditioning is on, a clogged filter is almost always where the investigation should start.

Placement is an important factor as well, particularly in open-plan environments. Units positioned close to entry doors or windows pull in more external air around seals and gaps, which limits how much filtering work they can realistically do. Where there's flexibility, intake positioning away from high-traffic entry points makes a practical difference.

This presents a strong case for regular, scheduled maintenance, rather than waiting for complaints. Most manufacturers recommend filter cleaning every four to six weeks during heavy-use periods, with a full service before each season. HVAC maintenance logs are worth including in routine health and safety audit checks - if a respiratory complaint later raises questions, documented maintenance history matters.

What to look for

If hayfever is a recurring issue for a noticeable number of staff, a brief audit of existing HVAC provision is a reasonable starting point. Key questions to ask are whether filters are being cleaned on schedule, whether units appropriately sized for the spaces they serve, and whether there are areas of the building where staff consistently report worse symptoms, which might point to coverage gaps or ventilation problems.

Tthree-function models - cooling, dehumidification, and fan-only - give the most flexibility across the year. Quieter units are worth prioritising for meeting rooms and focus areas where noise becomes a genuine productivity issue.

The broader point

Air conditioning in UK workplaces gets evaluated almost entirely on thermal comfort. Pollen season is a useful prompt to look at what the existing infrastructure is - or isn't - doing for air quality more broadly. A system that's well-specified, well-placed, and actually maintained is doing more occupational health work than most people credit it for.