Indoor Air Quality issues, often referred to as Tight Building Syndrome or Sick Building Syndrome, has become increasingly common since the energy crunch of the 1970s. As buildings were made tighter in order to seal in increasingly expensive conditioned air, indoor air pollutants were also sealed in. Sick Building Syndrome, along with intentionally decreased exhaust ventilation, the increased use of synthetic furnishings and building materials has made indoor air quality an important issue in public awareness.

Identification of Problems

Problem indoor environments can be traced to a variety of causes. NIOSH has determined that there are five major causes of indoor air quality problems:

  1. Ventilation system deficiencies
  2. Outside pollution sources
  3. Indoor pollution sources
  4. Biological contamination
  5. Building materials and furnishings

Common Indoor Air Pollutants


  1. Carbon Monoxide can enter the building either as vehicle exhaust or as the result of improper HVAC. Carbon Monoxide is an odorless, colorless, tasteless gas. Symptoms of low exposure include headaches, nausea, dizziness and fatigue. Higher exposure results in loss of consciousness
  2. Formaldehyde is characterized by a sharp, unpleasant odor. At very low concentrations it may be odorless. Formaldehyde exposure causes irritation to the eyes and mucus membranes. At present, the National Institute for Occupational Safety and Health (NIOSH) considers formaldehyde to be a suspect carcinogen (cancer-causing material).
  3. Tobacco smoke contains a wide variety of toxic and irritating compounds including, but not limited to, nicotine, carbon monoxide, formaldehyde, acrolein, particulate matter and radioactive materials studies have shown that passive inhalation of tobacco smoke, such as an indoor office environment, can be irritating and may cause adverse health effects.
  4. Radon gas is a naturally occurring radioactive gas. Radon and the materials it decays into, called radon daughters or radon decay products, increase the risk of lung cancer if they are inhaled.
  5. Asbestos is a known human carcinogen. Asbestos fibers can enter the air if asbestos-containing material is physically or chemically damaged, or otherwise removed. Exposure to low ambient concentration of asbestos is associated with increased incidence of lung cancer and mesothelioma, a fatal cancer of the chest wall lining.
    Ozone is an irritating gas, which affects the mucous membranes and the lungs. In outdoor air, ozone is formed by the action of sunlight on various air pollutants; inside it is formed primarily by copying machines and electrostatic air cleaners.
  6. Carbon Dioxide is produced by humans and exhaled from the lungs. Elevated levels place a mild stress on the body and result in people perceiving the air as “stuffy”. An elevated level can indicate that more fresh should be supplied by the ventilation system for the current occupant load of the building.
  7. Biological agents such as molds, yeasts, and bacteria can cause various reactions in exposed individuals. The major building systems, which facilitate growth of biological agents, also called viable particulate matter, are air conditioning systems and cool mist humidifiers. Molds and yeasts can cause mild to severe allergic reactions, while pathogenic, or disease-causing (generally bacteria) organisms, may be present in concentrations high enough to cause disease outbreaks.