How is building sickness different from a normal seasonal illness?

Seasonal illness travels with the person — a cold continues at home. Building-related symptoms resolve as soon as the affected building is left, and return within an hour of re-entry. The pattern is the signal.

Is stale office air always a sign of SBS?

Stale air is the most consistently reported precursor to SBS complaints. It almost always indicates CO₂ levels above 1,000 ppm, low outdoor air supply, or both — and it is the earliest sign that intervention is needed.

How many people need to be affected before it is treated as SBS?

The WHO threshold is 20% or more of occupants in the affected zone reporting two or more recognised symptoms that resolve on leaving. Below that threshold the cluster may still warrant attention, but above it a formal investigation is justified.

Recognising SBS

Signs of Sick Building Syndrome

Building sickness symptoms are real, reproducible and — crucially — patterned. Recognising the pattern early shortens the path from complaint to resolution.

Symptom-led Includes stale office air

Office desks at end of day with empty chairs

The pattern

What sets SBS apart from any other workplace complaint

The signs of sick building syndrome are individually unremarkable — headache, dry eyes, blocked nose, fatigue, difficulty concentrating. Taken alone, any of them could be a cold, a poor night's sleep or a stressful week. What makes them a diagnostic signal is the pattern they form together.

Three pattern markers separate building sickness symptoms from everything else. First, prevalence: a meaningful share of the workforce in one zone reports the same cluster of symptoms in the same week. Second, time-of-day: symptoms typically build through the working day and ease in the evening. Third — and most diagnostic — symptoms resolve when occupants leave the building. A colleague who works from home on Monday reports none of the symptoms; on Tuesday in the office, all of them return.

If your workforce is describing this pattern, you are not chasing a virus and you are not chasing morale. You are looking at a building.

Symptom clusters

The four families of building sickness symptoms

Cognitive symptoms

Difficulty concentrating, brain fog, mental fatigue, slower decision-making, more visible by mid-afternoon.

Sensory irritation

Dry, itchy or burning eyes, throat irritation, blocked or runny nose without any obvious infection.

Respiratory complaints

Persistent cough, chest tightness, exacerbation of mild asthma, particularly close to printers or in poorly ventilated rooms.

Skin and constitutional

Dry or itchy skin, headaches, fatigue and a general low-grade malaise that lifts in the evening or at weekends.

Stale office air

Why stale office air is the earliest warning

Before the headaches and the eye irritation arrive, the workforce notices the air. The lift lobby feels heavy by lunchtime. The meeting room is unbearable after the third occupant joins. A new starter remarks on the smell on their first morning and stops noticing it after a week. Stale office air is the leading indicator of every SBS investigation we have ever run.

Stale air is, almost always, CO₂ above 1,000 ppm and outdoor air supply below 8 l/s per person. It is the first parameter we measure, and the first that responds to remediation. A workplace that complains of stale air is a workplace that is telling you precisely where to look first.

FAQ

Signs of SBS — common questions

Headache, eye and throat irritation, fatigue, difficulty concentrating, dry skin and a perception of stale office air. The defining feature is that all of these symptoms improve once occupants leave the building.

Seeing these signs in your workplace?

An independent investigation establishes whether the pattern meets the WHO threshold — and what to do about it.

Request an investigation

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