Tech Page: Indoor Air Quality

According to the Environmental Protection Agency (EPA), people spend approximately 90% of their time indoors. This can be a problem if a home or office building has poor indoor air quality (IAQ). Some sources suggest that indoor air can be two to five times more polluted than outdoor air.

Some indoor air pollution sources include:

• Combustion sources — oil, gas, kerosene, coal, wood, and tobacco products, which can create nitrogen dioxide and carbon monoxide;
• Biological contaminants — bacteria, molds, mildew, pollen, animal dander, etc.;
• Outdoor sources — outdoor pollution, radon, and pesticides; and
• Building materials — Insulation that contains asbestos, new carpeting, and pressed-wood products can “off gas” chemicals.

If left untreated, these pollutants can cause health problems. Some of the more noticeable problems include irritation of the nose and throat, itchy eyes, headaches, fatigue, dizziness, and asthma.

Other health problems related to IAQ can be more serious. They include:

• Lung cancer — Over time, uranium in the ground beneath a home begins to break down and can release radon, a radioactive gas that is colorless and odorless. When radon seeps into the home in high levels, it can be breathed in and, over a number of years, can result in lung cancer. Radon levels can be tested with a radon test kit.
• Legionnaires’ disease — Legionella pneumophila is a type of bacteria that can inhabit water. When water droplets with the bacteria are inhaled, the disease is contracted and causes pneumonia. The disease can be fatal if it is not treated.

These pollutants can accumulate and can become more of a health hazard if a home or building does not have adequate ventilation rates. This can occur if a ventilation system has been installed or designed improperly.

Sick Building Syndrome

A building can also have inadequate ventilation if it has been constructed too tightly and allows for very little outside air to enter. This is called Sick Building Syndrome (SBS).

Air moves in and out of a dwelling in three ways:
1. Infiltration — Outside air enters the home through openings such as cracks and gaps in walls, floors, and ceilings, or through joints.
2. Natural ventilation — Air enters from doors and windows.
3. Mechanical ventilation — This can include various systems, from outdoor-vented fans to systems that work with the home’s heating and air conditioning system.

Clearing The Air

There are also three ways in which indoor air can be cleaned to reduce the amount of pollution in the air.
1. Source control — This is done by finding the source of the indoor air problems and eliminating or reducing the emissions. For example, if an appliance is emitting pollutants, it can be fixed to stop or control the output of pollution. This method is sometimes hard to apply because the source of the pollution cannot be identified.
2. Ventilation — This includes any kind of method to bring outside air into the building. This can be done in any of the ways previously mentioned.
3. Air cleaning — This can be used in conjunction with a ventilation system. A few specific methods can be used with a ventilation system to reduce indoor pollutants. Types of air cleaners include:

• Mechanical filters — These basic filters can be installed in the ducts of homes with central air conditioning and heating. They also come in two types, flat or extended surface. Flat panels (also known as panel filters) are made of fibers that capture larger particulates. Extended-surface or pleated cleaners have a larger surface area and are said to be more efficient in capturing particles, especially particles that can be breathed in.
• Electronic air cleaners — These air cleaners electrically charge particles in the ventilation system. When the particles are charged, they are drawn into a filter and trapped.
• Ultraviolet (UV) light — Living particles that cannot be trapped with a regular filter or with an electronic air cleaner can be killed with the use of UV lights.

More Ventilation Definitions

• Blowers: Fans or air-handling devices used to move air through the distribution system.
• Dampers: These are located in the ductwork and are responsible for regulating and zoning airflow. Dampers can zone airflow to certain rooms and locations. There are also fire and smoke dampers, which close under high temperatures to stop the spread of fire or smoke in the case of an emergency.
• Air handlers: These consist of the fan-blower, filter, and heat transfer coil. This device is responsible for blowing the air through the home.
• Valves: These components can be located in the ducts or on equipment; they allow for adjusting of air resistance.
• Grilles: Also known as registers, these are the covers over ducts that lead to the conditioned spaces.

For further information on IAQ, visit:
www.epa.gov/iaq
www.iaqa.org
www.ashrae.org

Publication date: 12/17/2001