Sick building syndrome
Some buildings quietly make people feel unwell, then better once they leave. Here is what sick building syndrome is, what causes it, and the practical fixes that resolve most cases.
Some buildings quietly make the people in them feel unwell. Staff arrive fine, develop headaches, tiredness and irritated eyes as the day wears on, then recover once they leave, only for it to happen again the next morning. When enough people in the same building report this pattern, it has a name: sick building syndrome. It is real, it is common, and most of its causes are fixable.
Sick building syndrome, or SBS, describes a cluster of symptoms that occupants link to time spent in a particular building and that ease after they leave. The World Health Organization frames it as a concern when more than around a fifth of a building's occupants report related symptoms. Crucially, it is not one disease with one cause. It is a pattern, headaches, fatigue, difficulty concentrating, and irritation of the eyes, nose, throat or skin, that points to something wrong with the indoor environment rather than to a specific infection. Conditions with a clear single cause, such as Legionnaires' disease or humidifier fever, are treated separately and are not classed as SBS.
What drives it
SBS is almost always multifactorial, which is exactly why it can be hard to pin down, but poor ventilation sits at the centre of most cases. When a building is sealed tight for energy efficiency without enough fresh air, occupant-generated carbon dioxide, moisture and odours accumulate, and so do pollutants from inside the building: volatile organic compounds off furniture, paint and cleaning products, fine particulate matter, formaldehyde from some materials, and ultrafine particles from printers and photocopiers. Add poorly maintained or badly balanced heating and air-conditioning, high indoor temperatures above the low twenties Celsius, low humidity, inadequate cleaning and poor lighting, and the risk rises. Mechanically ventilated, sealed offices are the classic setting.
The research points repeatedly back to fresh air. Analyses pooling many studies have found that as the outdoor air supply rate falls, the prevalence of SBS symptoms rises, with symptom rates climbing by roughly a quarter as the rate drops from around ten litres per second per person to five. Recirculating systems that reuse a large share of the air, stuck or wrongly set dampers, dirty filters and neglected cooling equipment all reduce genuine fresh air and concentrate whatever is in the building. There is often a human dimension too, high workload, low control over one's own temperature and lighting, and workplace stress are consistently associated with higher symptom reporting, which is why fixes work best when they address both the building and how people use it.
Because SBS has no single cause, the UK approach is investigative rather than prescriptive. Guidance long used by the HSE sets out sensible first steps for anyone facing suspected SBS: survey occupants to confirm symptoms are genuinely higher than expected, check general cleanliness and that vacuum cleaners and their filters are working, check cleaning materials are used correctly, and check the operation and maintenance of the heating and ventilation system, including that dampers are set correctly and the fresh-air supply is actually open. Only if symptoms persist after these basics is a more detailed environmental investigation, and specialist help, usually needed.
Fixing it in practice
The practical fixes follow the causes. Increase genuine fresh-air supply and make sure recirculation is not doing most of the work; service and correctly set the heating and ventilation system; change filters and clean the components that handle the air; manage temperature and humidity into a comfortable band; and cut indoor pollutant sources by choosing lower-emission materials and siting printers away from desks. Much of this is the ordinary maintenance a system needs anyway, and it overlaps with the reasons a hot, poorly ventilated space carries a hidden cost in comfort and staff wellbeing. The encouraging news is that most SBS causes respond to unglamorous, achievable action rather than expensive rebuilds.
Where the ductwork comes in
A recurring, overlooked contributor is the state of the ventilation ductwork itself. Ducts accumulate dust, grease and debris that both restrict fresh airflow and provide a reservoir of contaminants the system then distributes around the building, so a supposedly ventilated space can be quietly recirculating its own dirt. Cleaning the ductwork to recognised cleanliness standards is part of resolving SBS, which is also why there is a clear environmental case for cleaning ductwork rather than replacing it. A building cannot deliver healthy air through unhealthy ducts, however good the intentions of its ventilation design.
Questions
It is a pattern of symptoms, such as headaches, fatigue, poor concentration and irritated eyes, nose or throat, that occupants link to a particular building and that ease after they leave. The WHO associates it with buildings where more than around a fifth of occupants report symptoms.
It is usually multifactorial, but poor ventilation is central. Insufficient fresh air lets carbon dioxide, moisture, volatile organic compounds, particulates and printer emissions build up. Poorly maintained heating and air-conditioning, high temperatures, low humidity and workplace stress add to the risk.
Increase genuine fresh-air supply, service and correctly set the ventilation system, change filters, clean the components and ductwork that handle the air, manage temperature and humidity, and reduce indoor pollutant sources. Most causes respond to ordinary maintenance rather than major rebuilding.
No. Legionnaires' disease and humidifier fever have clear single causes and are treated as distinct illnesses. Sick building syndrome is a non-specific pattern of symptoms with no single identified cause, which is why investigation focuses on the whole indoor environment.
It can contribute. Ducts accumulate dust, grease and debris that restrict fresh airflow and harbour contaminants the system then spreads around the building. Cleaning ductwork to recognised cleanliness standards is part of resolving the problem and restoring healthy air.
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