The Causes of sick building syndrome 

Despite numerous investigations, no single cause has actually been established for sick building syndrome. Various experts have different theories: –

One theory suggests that chemicals travelling in the air enter the nose and affect an area of the brain called the limbic system. The limbic system plays a role in emotions, motivated behaviour, and memory, which may make a person more sensitive to a chemical odour it previously encountered.

Another theory suggests that the immune system is somehow damaged

Still another theory, called "toxic-induced loss of tolerance", suggests that acute or chronic exposure to chemicals causes some susceptible people to lose their tolerance for chemicals they previously could tolerate.

Other theories posit that fungi are primarily to blame, or that physical factors such as humidity, temperature, lighting, or the air-conditioning system are the cause.

None of these theories are proven but what is certain is that symptoms are more common in buildings with air-conditioning or mechanical ventilation. Six building features are strongly associated with symptoms of sick building syndrome (McIntyre and Sterling 1982):
1.A hermetically sealed, airtight shell
2.Mechanical heating, ventilation and air-conditioning systems
3.The use of materials and equipment that give off a variety of irritating and sometimes toxic fumes or dust
4.Fluorescent lighting that may produce photochemical smog
5.The application of energy conservation measures
6.Lack of individual control over environmental conditions

The following table summarises the types of problem found by the National Institute for Occupational Safety and Health (a US government organisation) in a study of 203 indoor air quality investigations: