Why Is IAQ Important?

In recent years, comparative risk studies performed by EPA and its Science Advisory Board (SAB) have consistently ranked indoor air pollution among the top five environmental risks to public health.

Good IAQ is an important component of a healthy indoor environment, and can help schools reach their primary goal of educating children.

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Understanding IAQ problems

Over the past several decades, exposure to indoor air pollutants has increased due to a variety of factors. These include the construction of more tightly sealed buildings; reduced ventilation rates to save energy; the use of synthetic building materials and furnishings; the use of personal care products, pesticides, and housekeeping supplies; and the increased use of vehicles and power equipment. In addition, activities and decisions, such as deferring maintenance to “save” money, can lead to problems from sources and ventilation.

The indoor environment in any building is a result of the interactions among the site, climate, building structure, mechanical systems (as originally designed and later modified), construction techniques, contaminant sources, building occupants, and outdoor mobile sources (cars, buses, trucks, and grounds maintenance equipment). This section contains a discussion on how these elements can cause IAQ problems, and Section 6: “Solving IAQ Problems” provides solutions. These elements are grouped into four categories:

  • Sources
  • Heating, Ventilation, and AirConditioning (HVAC) Systems
  • Pathways
  • Occupants
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sources of Indoor Air pollutants

Indoor air pollutants can originate within the building or be drawn in from outdoors. Air contaminants consist of numerous particulates, fibers, mists, bioaerosols, and gases. It is important to control air pollutant sources, or IAQ problems can arise—even if the HVAC system is properly operating. It may be helpful to think of air pollutant sources as fitting into one of the categories in the table on the following page, “Typical Sources of Indoor Air Pollutants.”

In addition to the number of potential pollutants, another complicating factor is that indoor air pollutant concentration levels can vary by time and location within the school building, or even a single classroom. Pollutants can be emitted from a variety of sources including:

  • Point sources (such as from science storerooms)
  • Area sources (such as newly painted surfaces)
  • Mobile sources (such as cars, buses, and power equipment)

resolving IAQ problems

Resolving IAQ problems involves diagnosing the cause, applying practical actions that either reduce emissions from pollutant sources, remove pollutants from the air (e.g., increasing ventilation or air cleaning), or both. Problems related to sources can stem from improper material selection or application, allowing conditions that can increase biological contamination and dust accumulation, or source location. Ventilation problems stem from improper design, installation, operation, or maintenance of the ventilation system. This Guide provides information on most IAQ problems found in schools, and does not require that pollutant measurements be performed and analyzed. It is important to take reported IAQ problems seriously and respond quickly:

  • IAQ problems can be a serious health threat and can cause acute discomfort (irritation) or asthma attacks.
  • Addressing an IAQ problem promptly is good policy. Parents are sensitive to unnecessary delays in resolving problems that affect their children. Staff have enough burdens without experiencing frustration over unresolved problems, and unaddressed problems invariably lead to greater complaints.
  • Diagnosing a problem is often easier immediately after the complaint(s) has been received. The source of the problem may be intermittent and the symptoms may come and go. Also, the complainant’s memory of events is best immediately after the problem occurs.

In some cases, people may believe that they are being adversely affected by the indoor air, but the basis for their perception may be some other form of stressor not directly related to IAQ. Section 6: “Solving IAQ problems,” discusses some of these stressors such as glare, noise, and stress.

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diagnosing IAQ problems

How to diagnose problems

The Problem Solving Checklist and the IAQ Problem Solving Wheel are your primary tools for finding solutions to problems. They will help simplify the process and lead the investigation in the right direction.

Start with the Problem Solving Checklist and encourage school staff to answer questions or perform activities posed by the checklist and the wheel. Pollutant sources and the ventilation system may act in combination to create an IAQ problem. Resolve as many problems as possible and note any problems that you intend to fix later.

Once you identify the likely cause of the IAQ problem, or the solution is readily apparent.

Spatial and timing patterns

As a first step, use the spatial pattern (locations) of complaints to define the complaint area. Focus on areas in the school where symptoms or discomfort have been reported. The complaint area may need to be revised as the investigation progresses. Pollutant pathways can cause complaints in parts of the school that are located far away from the source of the problems.

After defining a location (or group of locations), look for patterns in the timing of complaints. The timing of symptoms and complaints can indicate potential causes and provide directions for further investigation. Review the data for cyclic patterns of symptoms (e.g., worst during periods of minimum ventilation or when specific sources are most active) that may be related to the HVAC system or to other activities affecting IAQ in or near the school.

solving IAQ problems

1. Source Management: 

Managing pollutant sources, the most effective control strategy, includes:

• Source removal – Eliminating or not allowing pollutant sources to enter the school. Examples include not allowing buses to idle, especially not near outdoor air intakes, not placing garbage in rooms with HVAC equipment, and replacing moldy materials.

Source reduction – Improving technology and/or materials to reduce emissions. Examples include replacing 2-stroke lawn and garden equipment with lower emitting options (e.g., manual or electrically powered or 4-stroke); switching to low emissions portable gasoline containers; and implementing technology upgrades to reduce emissions from school buses.

Source substitution – Replacing pollutant sources. Examples include selecting less- or non-toxic art materials or interior paints.

Source encapsulation – Placing a barrier around the source so that it releases fewer pollutants into the indoor air. Examples include covering pressed wood cabinetry with sealed or laminated surfaces or using plastic sheeting when renovating to contain contaminants.

2. Local Exhaust – Removing (exhausting fume hoods and local exhaust fans to the outside) point sources of indoor pollutants before they disperse. Examples include exhaust systems for restrooms and kitchens, science labs, storage rooms, printing and duplicating rooms, and vocational/industrial areas (such as welding booths and firing kilns).

3. Ventilation – Lowering pollutant concentrations by diluting polluted (indoor) air with cleaner (outdoor) air. Local building codes likely specify the quantity (and sometimes quality) of outdoor air that must be continuously supplied in your school. Temporarily increasing ventilation as well as properly using the exhaust system while painting or applying pesticides, for example, can be useful in diluting the concentration of noxious fumes in the air. 

4. Exposure Control – Adjusting the time and location of pollutant exposure. Location control involves moving the pollutant source away from occupants or even relocating susceptible occupants.

Time of use – Avoid use of pollutant sources when the school is occupied. For example, strip and wax floors (with the ventilation system functioning) on Friday after school is dismissed. This allows the floor products to off-gas over the weekend, reducing the level of pollutants in the air when the school is reoccupied on Monday. Another example is to mow around the building and near play fields only before or after school hours.

Amount of use – Use air-polluting sources as little as possible to minimize contamination of the indoor air.

Location of use – Move polluting sources as far away as possible from occupants or relocating susceptible occupants. 

5. Air cleaning – Filtering particles and gaseous contaminants as air passes through ventilation equipment. This type of system should be engineered on a case-by-case basis.

6. Education – Teaching and training school occupants about IAQ issues. People in the school can reduce their exposure to many pollutants by understanding basic information about their environment and knowing how to prevent, remove, or control pollutants.