Can poor ventilation in the office really make people unwell?

Yes. Once CO₂ climbs above 1,000 ppm, cognitive performance measurably declines; above 1,400 ppm, headache, fatigue and difficulty concentrating become statistically common. Bioeffluents, VOCs and particulates accumulate in parallel.

Is bad indoor air quality always to blame?

In almost every confirmed SBS investigation the cause is environmental. Lighting, acoustics and ergonomic stressors can amplify symptoms but the trigger is overwhelmingly the air, the ventilation regime or the materials that are off-gassing into the space.

Why do problems often start after a refurbishment?

New flooring, adhesives, paints and furniture release a peak of formaldehyde and other VOCs that takes weeks to months to decay. If ventilation rates were not increased to accommodate the new emissions, occupants notice the change within days of reoccupation.

Background

Causes of Sick Building Syndrome

Sick building syndrome rarely traces to a single agent. It emerges from a small number of compounding engineering and operational causes — almost all of them correctable.

Engineering-led Evidence-based

Context

Why modern buildings produce the SBS pattern

The historical preconditions for sick building syndrome are well documented. Sealed buildings constructed from the 1980s onwards, fitted with fixed-rate mechanical ventilation, internal finishes that off-gas formaldehyde and other volatile organic compounds, and maintenance regimes that lapsed within the first decade of life. The modern equivalent is the airtight Part L office: insulated, sealed, and reliant on mechanical ventilation that is often under-sized for the way the building is actually used.

Occupancy density has become the new amplifier. Hybrid working compresses occupancy into the middle of the week. Original ventilation designs are asked to do more on a Tuesday than they were ever sized for. The complaints follow the same pattern — quiet Mondays and Fridays, symptomatic mid-week — and that pattern is now a recognisable diagnostic signal for poor ventilation in the office.

Bad indoor air quality is not a single thing. It is the compounding effect of ventilation, sources, materials and moisture, and it is the job of an SBS investigation to disentangle them.

The five recurring causes

What we find in almost every SBS investigation

Poor ventilation in the office

Outdoor air supply below 10 l/s per person, demand-controlled ventilation overridden, or AHUs operating in part-load when occupancy has spiked. The dominant cause in UK SBS investigations.

Contaminated HVAC

Dirty cooling coils, biofilm in drip trays, dust loading in supply ducts and degraded filters push microbial and particulate exposure into the supply air itself.

Material off-gassing

Formaldehyde and VOC emissions from recent refurbishment, new furniture, carpets, adhesives and paints. The classic post-fit-out complaint pattern.

Humidity extremes

Below 30% RH dries mucous membranes; above 60% RH amplifies dust mites and mould. Both ends of the range drive sensory irritation directly.

Localised source proximity

Printer banks, kitchenettes, photocopier rooms vented into the open-plan area, and cleaning chemistry concentrate exposure for nearby desks without affecting the building average. Symptom mapping by desk location reveals it quickly.

The diagnostic signal

When poor ventilation in the office becomes bad indoor air quality

The transition from "poor ventilation" to "bad indoor air quality" is rapid. At 600 ppm CO₂ — a well-ventilated office — occupants describe the air as fresh. By 1,000 ppm, fatigue and headache begin to appear in measurable studies. By 1,500 ppm — common in busy meeting rooms — cognitive performance has measurably declined and SBS-style complaints become statistically common.

The CO₂ value is not itself the problem. It is the proxy that tells you bioeffluents, VOCs and particulates are accumulating at the same rate. Increasing outdoor air supply is the single intervention with the largest effect on SBS symptom reports.

Beyond ventilation, the next two causes — contaminated HVAC and material off-gassing — explain almost everything that ventilation alone cannot. A planned inspection of the AHU and a speciated VOC test together cover the residual cases.

FAQ

Causes of sick building syndrome — common questions

Under-ventilation — outdoor air supply below 10 l/s per person. It is the cause in the majority of UK office investigations and is almost always coupled with one or two of the other root causes.

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