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Construction, Part of Indoor Air Quality Design Tools for Schools


Introduction

Poor job-site construction practices can frustrate even the best design by allowing moisture and other contaminants to become potential long term problems. Preventive job-site practices will reduce the potential for residual problems with indoor air quality in the completed building and reduce undue health risks for workers.

The costs of poor indoor air quality are difficult to quantify, but considerable. They are the sum of illness and decreased student productivity paid by students and teachers, along with the district's cost of equipment replacement, workers compensation claims and in the most severe cases, potential litigation.

Unfortunately, serious health complaints have resulted from careless acts during construction projects, such as failure to clean up spilled adhesives or to properly ventilate during and after applying sealants in an occupied building. These mistakes have led to unpleasant headlines and costly lawsuits. Good IAQ strategies during construction will help eliminate these potential liabilities.

Risk managers may be reluctant to take on the added responsibility of indoor air quality planning and preventive job-site practices. However, school districts and project architects across the country have experienced litigation related to poor indoor air quality resulting from construction activities. Addressing these issues before and during construction will reduce exposure of the district and designers to potentially expensive litigation in the future.

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IAQ Management During Construction Planning

Checklist Task
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Incorporate indoor air quality goals into the bid and construction documents.
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Ensure that all members of the project team are knowledgeable about indoor quality issues and have defined responsibilities for implementation of good indoor air quality practices.
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Require the development and use of an indoor air quality management plan. The purpose of the management plan is to prevent residual problems with indoor air quality in the completed building and protect workers on the site from undue health risks during construction. The plan should identify specific measures to address:
  • Problem substances, including:
    • construction dust
    • chemical fumes
    • off-gassing materials
    • moisture
    The plan should ensure that these problems are not introduced during construction, or, if they must be, eliminates or reduces their impact.
  • Areas of planning, including:
    • product substitutions and materials storage
    • safe installation
    • proper sequencing
    • regular monitoring
    • safe and thorough cleanup
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Conduct regular inspection and maintenance of indoor air quality measures including ventilation system protection and ventilation rate.
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Conduct safety meetings, develop signage and establish subcontractor agreements that communicate the goals of the construction indoor air quality plan. The indoor air quality construction plan is also a good opportunity to proscribe behaviors unacceptable to the owner that represent a potentially negative impact on long term indoor air quality such as smoking, using chew tobacco, or wearing contaminated work clothes.
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Require contractors to provide information on product substitutions sufficient to enable operations and maintenance (O&M) staff to properly maintain and repair materials in place.

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Construction Practices

During school construction there are several simple actions contractors can perform that will minimize the potential for indoor air quality problems. Trades that need to be especially careful include:

  • flooring
  • roofing
  • painting
  • HVAC
  • insulators
  • the clean-up crew
Checklist Task
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Keep building materials dry. Building materials, especially those with moisture absorbing properties like wood, insulation, paper and fabric, should be kept dry to prevent the growth of mold and bacteria. If moisture is present, mold will grow on any virtually any material. Some building materials such as wood may arrive at the construction site with a high moisture content or may have been wetted before arrival or during the transport process.

Wet materials need to be allowed to dry as much as possible as weather permits. Cover dry materials with plastic to prevent rain damage and if resting on the ground, use spacers to allow air to circulate between the ground and the materials.

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Dry water damaged materials quickly. Water damaged materials should be dried within 24 hours. Due to the possibility of mold growth, materials that are damp or wet for more than 72 hours may need to be discarded.
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Clean spills immediately. If solvents, cleaners, gasoline, or other odorous or potentially toxic liquids are spilled onto the floor, they should be cleaned up immediately. If a spill occurs on an easily replaced building material, it may be safest to discard it and replace it with new material. Odors from significant spills can linger sometimes for years, causing comfort and health problems for the future occupants of the school.
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Seal unnecessary openings. Seal all unnecessary openings in walls, floors and ceilings that separate conditioned space (heated or cooled) from unconditioned space. For example, it is common to punch large holes in the floor to allow pipes and wires to run between the rooms above and the crawlspaces or tunnels below. These oversized openings can cause two significant indoor air quality problems. Air that is contaminated with mold, radon, moisture and pesticides can easily enter the rooms; and pests such as roaches or rodents can enter the rooms, leaving behind odors and allergens.
Checklist Task
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Temporarily seal duct-work. As duct-work is being installed, all return and supply air vents and any open duct-work should be temporarily sealed to prevent the duct-work and air handling units from being contaminated with construction debris or dust.
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Ventilate when needed. Some construction activities can release large amounts of VOCs into the school and if the school is already enclosed with walls, windows and doors, outdoor air can no longer easily flow through the building and remove the VOCs. In addition to affecting the health of the construction workers, these VOCs can also be adsorbed onto other building materials and be re-released into the air later when the school is occupied by children and staff. During certain construction activities, temporary ventilation systems should be installed to quickly remove the gases.

Ventilation is generally needed when "wet" building materials are in use, when using materials that give off an odor, or when using materials that carry a manufacturer's warning regarding the need for ventilation. Odors from building materials are the result of chemicals being released from the materials into the air, so if there is an odor present, it is safest to provide ventilation that will quickly remove those odors from the building.

Examples of potentially problematic construction activities include painting (even with no- or low-VOC paints), spreading of floor adhesives and use of large amounts of caulk, sealants and cleaning agents. Additionally, the installation of large amounts of building materials, such as carpet or vinyl-based flooring products and composite wood cabinets and shelves, can require extra ventilation if the material has not been carefully selected or aired-out before being unrolled or unpackaged within the school.

Checklist Task
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During installation of carpet, paints, furnishings and other VOC-emitting products, provide supplemental (spot) ventilation for at least 72 hours after work is completed.

It is important that an exhaust fan be used to pull the polluted air out of the building, not to push outdoor air into the building. Simply opening windows or doors is not enough to effectively exhaust contaminants in most cases. The fan should be placed in a window or exterior door as close to the work area as possible and any openings in the window or door around the fan be temporarily sealed with plastic or cardboard.

Then open a window or exterior door at the opposite end of the room or building, so that fresher outdoor air will flow across the work area and sweep polluted air out through the exhaust fan. The size of exhaust fan needed will increase as the size of the room increases and as the amount of gases being released into the air increases. The fan should provide about 5 air changes per hour (5 ACH).

Divide the volume of the room in cubic feet by 12 to get the minimum amount of cubic feet per minute (CFM) that the fan must be able to exhaust. For example, a classroom with a volume of 9000 cubic feet (1000 square feet of floor area with 9 foot ceilings) divided by 12 results in a fan of 750 CFM. A 21 inch box fan may be sufficient for a single classroom if the materials are not too strong a source of gases, but would certainly not be sufficient for a wing or a whole school.

As a rule of thumb, there may be enough airflow if odors do not spread out of the immediate area where the work is being performed, of if dust or smoke released into the air can be seen to be drawn towards the exhaust fan. As long as the odors or air pollutants are present, the temporary exhaust ventilation must continue to be operated, even during nights and weekends if necessary. Ventilation should continue for a minimum of 24 hours after completion, or until there are no longer any noticeable odors.

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Require respirators designed to protect workers installing VOC-emitting products (interior and exterior).
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Reduce construction dust. Minimize the amount of dust in the air and on surfaces. Examples include use of vacuum assisted drywall sanding equipment and use of vacuums instead of brooms to clean construction dust from floors.
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Use wet sanding for gypsum board assemblies.

Exception: Dry sanding is acceptable if the following measures are taken:

  • Full isolation of space under finishing
  • Plastic protection sheeting is installed to provide air sealing during the sanding
  • Closure of all air system devices and ductwork
  • Sequencing of construction precludes the possibility of contamination of other spaces with gypsum dust
  • Worker protection is provided. Use safety meetings, signage and subcontractor agreements to communicate the goals of the construction indoor air quality plan.
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Avoid use of combustion equipment indoors. Engines and heaters that run on gasoline, diesel, kerosene, or other fossil fuels should not be operated indoors unless absolutely necessary and only when large quantities of exhaust ventilation are provided to remove combustion pollutants such as carbon monoxide and moisture.
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Store liquids outdoors. To reduce the possibility of spills during storage, transfer, or mixing, store all odorous or toxic liquids outside the building and protect against freezing.
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Use less toxic cleaning agents. Ensure that the cleaning crews do not use highly toxic or odorous cleaning agents inside the school.
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Consider a building flush-out at the end of the construction process and before occupancy.

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References and Resources

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