Indoor Air Quality and Ventilation

Risk-Tex Articles

"Indoor Air Quality Seminar" Nov. 2005 issue "Are You Breathing Quality Air at Work?" July 2003 issue "Mold Making News: Indoor Air Quality Becoming Hot Topic" Aug. 2001 issue

The quantity and severity of health problems caused by the poor quality of indoor air has increased over the last 15 years. This is attributed to many factors. Most Americans spend up to 90 percent of their time indoors and many spend most of their working hours in an office environment. Studies conducted by the U.S. Environmental Protection Agency and others indicate that indoor environments sometimes can have levels of pollutants that are actually higher than levels found outside. To lower energy costs, buildings are often sealed better to prevent infiltration of outside air, and the amount of fresh air added to buildings via ventilation systems can be significantly decreased. To lower material and construction costs, as well as to provide for easy care, products are sometimes used that emit toxic and irritating vapors. As a result, employees may experience headaches, nausea, sinus congestion, dizziness, and several other physical problems both at home and at work. There is no single manner in which these health problems appear. In some cases, problems begin soon after workers enter their offices and diminish soon after workers leave (typically called sick building syndrome). At other times, symptoms continue until the illness is treated (typically called building-related illnesses). Sometimes there are outbreaks of illness among many workers in a single building. In other cases, health symptoms show up in only certain employees.

• Sources of Indoor Air Problems in Offices
• Ventilation Systems
• Building Use
• Building Surveys/Inspections
• Guidelines for Loss Prevention and Control

Three major reasons for poor indoor air quality in office buildings are the following:

• 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.

The most important factor influencing indoor air quality (IAQ) is the presence of pollutant sources. Common sources of office pollutants include the following:

• Environmental tobacco smoke;
• Asbestos from insulation and fire-retardant building supplies;
• Formaldehyde from pressed wood products;
• Other organics from building materials, carpeting, and similar office furnishings;
• Cleaning materials and related activities;
• Restroom air fresheners;
• Paints and adhesives;
• Copying machines, photography, and print shops;
• Biological contaminants from dirty ventilation systems or water-damaged walls, ceilings, and carpets; and
• Pesticides generated by pest management practices.

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. Ventilation systems can contribute to indoor air problems in several ways when these systems are poorly designed, operated, or maintained.

For example, problems may 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 outside air does not actually reach the breathing zone of building occupants. Improperly located outside air intake air vents can also bring in air contaminated with automobile and truck exhaust, boiler emissions, fumes from dumpsters, or air vented from restrooms. 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 ductwork.

Buildings originally designed for one purpose may end up being converted for use as office space. While new structures are normally used according to the designer's plan, as time passes renovations occur, building machinery is changed or replaced, the occupants engage in different activities, and systems degrade. If not properly modified during building renovation, room partitions and ventilation systems may contribute to IAQ problems by restricting air recirculation or by providing an inadequate supply of outside air.

Each of these stages of a building's life can present different IAQ problems. New buildings frequently suffer from IAQ problems due to the off-gassing of irritants from structural materials and furnishings. Middle-aged buildings often have a significant amount of asbestos within the structure. The problems in older buildings commonly result from antiquated mechanical systems that fail to provide uniform heating and cooling and grow microorganisms that are spread through the system. To measure the quality of air in a building, a building survey inspection should be conducted.

Building surveys are a set of procedures used to evaluate the current performance of a building and to predict the quality of future performance. These procedures are useful in all stages in the life of a building, but are of most use when a problem has been identified. For indoor air quality survey and inspection information, Texas state agencies should contact the Texas Department of State Health Services or retain the services of a commercial indoor air quality inspection firm.

It is best to work with one individual agency or firm that is able to handle the project from start to finish. A qualified agency or firm will be able to provide a comprehensive report with details on how to approach remediation, including specific design recommendations and cost estimates.

Recommendations from a qualified IAQ inspector will typically center around six approaches to controlling IAQ problems. These include the following:

• Outside air supply;
• Contaminant source control;
• Contaminant source substitution;
• Policy implementations;
• Air distribution; and
• Filtration.

If sufficient information and recommendations have been obtained from the building survey to identify the problem(s) or source of concern, corrective action can be taken. Depending upon the complexity of the problem, it may be necessary for management to call in expert help, such as that of an engineering/ventilation consultant or an industrial hygienist. Early recognition of a problem and a timely and systematic evaluation of the problem are key factors to a quick and effective resolution of IAQ problems or concerns.