Health Problems Due to Poor Indoor Air Quality (IAQ)

During the 1970s, the energy crisis drew attention on the topic of energy conservation, and homes were built with improved insulation. Office buildings minimized the introduction of fresh air to reduce energy costs. Building renovations were focused on being energy efficient, rather than on ensuring proper ventilation systems were in place to ensure fresh air is being circulated in the indoor space. These changes in construction sparked by the interest in energy conservation increased the number of contaminants that accumulated indoors and reduced the amount of fresh air available to maintain adequate indoor air quality (IAQ). If too little outdoor air enters an indoor environment, pollutants can accumulate to levels that can pose health and comfort problems. Climate or weather conditions with high humidity can increase pollutant levels even more. The combination of poor ventilation and increased pollutant levels lead to Sick Building Syndrome.

Outdoor air can enter a building through infiltration, natural ventilation and mechanical ventilation. Infiltration occurs when outdoor air flows through joints and cracks in a home or building. Natural ventilation occurs when wind blows through open windows and doors, and mechanical ventilation takes place in the form of outdoor-vented fans for a single room such as a bathroom or kitchen, and systems that use fans and duct work to continuously remove indoor air and distribute filtered and conditioned outdoor air to the indoor environment.

The rate at which outdoor air replaces indoor air is called the air exchange rate, and when this rate is low, the risks of developing problems related to the indoor environment increase. Many adverse health effects associated with indoor air pollution due to poor ventilation and poorly maintained HVAC systems range from decreased worker productivity, respiratory illness, cancer and in the most extreme cases, death.

In 1976 there was an outbreak of Legionnaires' Disease at an American Legion, in which 221 people contracted the disease from breathing air contaminated by bacteria originating from the building's air conditioner. The Department of Health and Human Services Center for Disease Control and Prevention (CDC) estimates that at least 18,000 people contract Legionnaires' disease every year in the United States alone. Approximately 5-30% of those that contract the disease will die. The Legionnaire bacteria (Legionella pneumophila) is only harmful when inhaled resulting in severe pneumonia, but presents a strong case for the importance of regular cleaning and maintenance of HVAC systems.