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Most people are aware that outdoor air pollution can damage their health but may not know that indoor air pollution can also have significant effects. EPA studies of human exposure to air pollutants indicate that indoor air levels of many pollutants may be 2-5 times, and occasion more than 100 times, higher than outdoor levels. These levels of indoor air pollutants are of particular concern to school engineers because of our roles as operating engineers in schools.
In recent years, comparative risk studies performed by EPA and its Science Advisory Board have consistently ranked indoor air pollution among the top five environmental risks to public health.
Three major reasons for poor indoor air quality in buildings are the presence of indoor air pollution sources; poorly designed, maintained, or operated ventilation systems; and uses of the building that were unanticipated or poorly planned for when the building was designed or renovated.
As with homes, the most important factor influencing indoor air quality is the presence of pollutant sources. Commonly found school pollutants and their sources include organics from building materials, carpet, and other office furnishings, cleaning materials and activities, restroom air fresheners, paints, adhesives, copying machines, and photography and print shops; biological contaminants from dirty ventilation systems or water-damaged walls, ceilings, and carpets; pesticides from pest management practices; environmental tobacco smoke; asbestos from insulating and fire-retardant building supplies; and formaldehyde from pressed wood products.
Mechanical ventilation systems in large buildings are designed and operated not only to heat and cool the air, but also to draw in and circulate outdoor air. If they are poorly designed, operated, or maintained, however, ventilation systems can contribute to indoor air problems in several ways. For example, problems arise when, in an effort to save energy, ventilation systems are not used to bring in adequate amounts of outdoor air. Inadequate ventilation also occurs if the air supply and return vents within each room are blocked or placed in such a way that outdoor air does not actually reach the breathing zone of building occupants. Improperly located outdoor air intake vents can also bring in air contaminated with automobile and truck exhaust, boiler emissions, fumes from dumpsters, or air vented from restrooms. (See Chicago Municipal Codes)
Finally, ventilation systems can be a source of indoor pollution themselves by spreading biological contaminants that have multiplied in cooling towers, humidifiers, dehumidifiers, air conditioners, or the inside surfaces of ventilation duct work.
Indoor air pollutants can be circulated from portions of the building used for specialized purposes, such as lunchrooms, kitchens, boiler rooms, janitor’s closets, print shops, and auto shops into classrooms in the same building. Carbon monoxide and other components of automobile exhaust can be drawn from underground parking garages through stairwells and elevator shafts into office spaces.
In addition, buildings originally designed for one purpose may end up being converted to use as office space. If not properly modified during building renovations, the room partitions and ventilation system can contribute to indoor air quality problems by restricting air recirculation or by providing an inadequate supply of outdoor air.
Usually the most effective way to improve indoor air quality is to eliminate individual sources of pollution or to reduce their emissions. Some sources, like those that contain asbestos, can be sealed or enclosed; others, like gas stoves, can be adjusted to decrease the amount of emissions. In many cases, source control is also a more cost-efficient approach to protecting indoor air quality than increasing ventilation because increasing ventilation can increase energy costs. Specific sources of indoor air pollution in your home are listed later in this section.
Another approach to lowering the concentrations of indoor air pollutants in your home is to increase the amount of outdoor air coming indoors. Most home heating and cooling systems, including forced air heating systems, do not mechanically bring fresh air into the house. Opening windows and doors, operating window or attic fans, when the weather permits, or running a window air conditioner with the vent control open increases the outdoor ventilation rate. Local bathroom or kitchen fans that exhaust outdoors remove contaminants directly from the room where the fan is located and also increase the outdoor air ventilation rate.
It is particularly important to take as many of these steps as possible while you are involved in short-term activities that can generate high levels of pollutants--for example, painting, paint stripping, cooking, or engaging in maintenance and activities such as welding, soldering, or sanding. You might also choose to do some of these activities outdoors, if you can and if weather permits.
The effectiveness of an air filter depends on how well it collects pollutants from indoor air (expressed as a percentage efficiency rate) and how much air it draws through the cleaning or filtering element (expressed in cubic feet per minute). A very efficient collector with a low air-circulation rate will not be effective, nor will a cleaner with a high air-circulation rate but a less efficient collector. The long-term performance of any air filter depends on maintaining it according to the manufacturer's directions. Air cleaners are generally not designed to remove gaseous pollutants.
Engineers are encouraged to obtain a copy of Building Air Quality: A Guide for Building Owners and Facility Managers. Building Air Quality is simply written, yet provides comprehensive information for identifying, correcting, and preventing indoor air quality problems. BAQ also provides supporting information such as when and how to select outside technical assistance, how to communicate with others regarding indoor air issues, and where to find additional sources of information. BAQ is available for $24 from U.S. GPO, Superintendent of Documents, P.O. Box 371954, Pittsburgh, PA 15250-7954; stock #055-000-00390-4 or call (202) 783-3238.
This report was assembled by George Kelly, operating engineer with the Chicago Public School system from many sources including EPA documents.