New materials and for example regulatory fire retardant treatments often include chemical compounds which on their own or in small quantities may not present a health problem but which in combination or increased amounts may do so.
Air currents within a building may blend together molecules of chemical compounds and gases into a toxic cocktail which is then frequently inhaled. The effects of long term inhalation of the same or recycled air of contaminated quality are being researched and established by specialists. Links are being identified with chronic illnesses and the environment in which we live.
External air monitoring and quality by environmentalist engineers brought about an improvement in health by control over chemical and pollution emissions from industry. It is only recently that the micro climate inside a building has begun to receive attention.