By Susan McClendon
What are VOCs, where do they come from, and why are they a problem?
VOCs are produced both naturally and artificially. Some are also greenhouse gases, some are toxic, and some are carcinogens. Outdoors, some VOCs react with other chemicals in the air to form ground-level ozone, causing respiratory problems. Indoors, VOC concentrations have been found to be consistently two to five times higher than outdoors. Once the VOCs get into the indoor air the only way to reduce the concentration is by ventilation.
VOC: Volatile Organic Compound Organic: Molecules containing carbon atoms Volatile: Vaporizes (evaporates) at normal temperature and pressure |
Prevention includes prohibiting tobacco smoking and minimizing activities that use chemicals (cleaning supplies, copy machines, pesticides, solvent-based paints and adhesives). When the use of chemicals indoors cannot be avoided, the rooms they are used in can be sealed and separately ventilated—these include large-capacity copy machines, janitor closets where cleaning compounds are mixed, laboratories, and cooking and combustion sources.
Prevention also includes using building materials that are low-emitting, nonirritating, nontoxic, and chemically inert. This is especially important in schools because children are more susceptible than adults to indoor air pollutants. Some materials off-gas dramatically when they are first manufactured (e.g. the "new car smell" of vinyl)—a 2-week ventilation "flush out" prior to occupancy is one solution for this. Other materials continue to emit VOCs for their lifetime.
Regulations Limiting VOCs
The first U.S. standard restricting VOC content was established by the U.S. Environmental Protection Agency (EPA) to address the Clean Air Act of 1970. The EPA definition of VOCs is: "Volatile organic compounds (VOC) means any compound of carbon, excluding carbon monoxide, carbon dioxide ... which participates in atmospheric photochemical reactions. This includes any such organic compound other than the following, which have been determined to have negligible photochemical reactivity." This is followed by a long list. The potential contribution that each VOC makes to ozone formation depends on its photochemical reactivity—that is, its tendency to participate in photochemical reactions in the atmosphere in ways that contribute to ozone formation. The point of EPA's regulations is to reduce sources of outdoor air pollution, particularly ozone. (Note that the greenhouse gas effect is not addressed at all, as the most significant greenhouse gases are exempt from these regulations because they don't contribute to the formation of ground-level ozone.)
40 CFR 59, part of the Code of Federal Regulations, is titled National Volatile Organic Compound Emission Standards for Consumer and Commercial Products. Subpart D (40 CFR 59.400-413) is National Volatile Organic Compound Emission Standards for Architectural Coatings, which covers many types of coatings, including paints, stains, concrete-curing compounds, paint-on wood preservatives, transparent sealers, and water repellents. At the time these regulations were first enacted most of those types of coatings were solvent-borne liquids. The solvents were almost all VOCs and the point of using a solvent as the vehicle was that it was volatile and would cure the coating by evaporation. This regulation requires that all products of this type manufactured for sale in the United States be made with a maximum total VOC content as specified in the regulation, with the intent to reduce a large source of emitted VOCs. Many of these coatings have been reformulated, either by reducing their VOC content or by changing the vehicle to water. Water-based paints have been dramatically improved but some water-based coatings simply don't perform as well as their solvent-based counterparts. Some coatings that do not meet the federal EPA requirements are still made and imported under an exception whereby the manufacturer pays an "exceedance fee," which is inevitably passed on to the buyer.
The method of determining the VOC content under the EPA and similar regulations is ASTM D 2369, which measures the mass of VOCs in relation to the volume of the coating, measured in grams per liter. Product literature for these products will show a g/L value in the range of 120 to almost 900—the regulation specifies different limits for different coatings, acknowledging that the technology didn't exist at the time to reduce the content farther. The U.S. EPA has not substantially changed its limits over the years. State and local air quality management districts have been established and follow the EPA model but often reduce the limits substantially. Because the federal regulations apply to everyone, this was the model for VOC content restrictions for many years, focusing on the big offenders using what are essentially arbitrary limits. More recently, the relative reactivity of VOCs has been researched, with the goal of identifying those VOCs that it would be best to concentrate on for ozone reduction. This treats the issue as one of reducing the "process" source of VOCs—during the installation process—but not the installed products as ongoing emission sources.
Besides using a small chamber test, this standard uses a completely different method of determining compliance that is based on health effects instead of arbitrary content limits. First, the materials are tested for chemicals that have been classified as hazardous air pollutants, carcinogens, and reproductive or developmental toxins. The lists of these chemicals are specified in the test method and may be found at several state agency websites. After determination of the VOC content, the method calls for modeling the results to represent airborne concentrations that would be present in buildings. Two standard scenarios are specified—for school classrooms and for office spaces—modeling typical products such as floor coverings, wall coverings, paint, and suspended ceilings. Because there are likely to be multiple sources of VOCs in a building, an individual product is allowed to contribute no more than one-half the permitted concentration. The estimated building concentrations are compared to one-half of the noncancer Chronic Reference Exposure Level (CREL) of the chemical. CRELs are inhalation concentrations to which the general population, including sensitive individuals, may be exposed for long periods (10 years or more) without the likelihood of serious adverse systemic effects other than cancer.
The simple way to implement low-VOC specifications is to follow either the LEED or CHPS rating systems. These constitute recommendations for which types of materials to restrict because they are likely to contain VOCs. The rating systems give credits if all the products in a particular category comply with the low-VOC criteria. For LEED-NC and -CS, the categories are: 1) paints and coatings, 2) adhesives and sealants, 3) carpet and carpet adhesives, and 4) composite wood and agrifiber products. LEED-CI adds one category: systems furniture and seating. LEED for Schools changes the carpet category to include all flooring and adds classroom furniture, desks and seating, and ceiling and wall materials. The products covered by LEED for Schools' categories are virtually identical to those covered by the CHPS rating system but with a different number of credits. LEED-NC, -CS, and -CI do not use "the California method." Instead, they use older, more empirical methods, including EPA-style arbitrary criteria. However, because the California method is designed to predict consequences inside buildings more accurately and because it uses health-related criteria, it seems unlikely that products complying with that method would not qualify for the corresponding credits for the nonschools LEED certifications.
Paints and Coatings: Compliant products are widely available. Manufacturers have been making paints and coatings to the EPA and more stringent rules for many years. High-quality water-based paints are available. Some paints are included on the CHPS Low Emitting Materials List. Some have been certified by third-party organizations.
Adhesives and Sealants: Compliant products are widely available. Manufacturers have been making adhesives and sealants to EPA-style rules for many years. High-quality sealants with zero-VOC content are available. Some are included on the CHPS Low Emitting Materials List. Some have been certified by third-party organizations.
Carpet and Carpet Adhesives: Compliant products are widely available. Manufacturers have been making both carpet and carpet adhesives to the Carpet and Rug Institute's Green Label Plus Certification for many years. CHPS and LEED for Schools also accept the CRI Green Label Plus.
Composite Wood and Agrifiber: The principal concern is urea-formaldehyde content. Small amounts of formaldehyde are present in most indoor environments. Itching of the eyes, nose, or throat may indicate an elevated concentration. OSHA regulates formaldehyde, a specific VOC, as a carcinogen. OSHA has adopted a Permissible Exposure Level (PEL) of 0.75 ppm and an action level of 0.5 ppm. HUD has established a level of 0.4 ppm for mobile homes. According to the EPA, it is advisable to mitigate formaldehyde that is present at levels higher than 0.1 ppm. Formaldehyde occurs naturally in smoke from forest fires, in smog, and artificially in automobile exhaust and tobacco smoke. Most formaldehyde produced industrially is used to make polymers and other chemicals. Adhesives, such as those used to laminate plywood or bind particleboard, and melamine resin, used to make plastic laminates, are commonly made from formaldehyde. LEED offers a credit for not using any composite wood or agrifiber products made with added urea-formaldehyde. CHPS includes testing for formaldehyde in the standard test. Products are available but not universally.
Furniture: Compliant products are available. Check the CHPS list and third-party certification programs for type required.
Ceiling and Wall Materials: Some compliant products are available but coverage is spotty. Check the CHPS list and third-party certification programs for type required.
Both LEED and CHPS give credit for doing a building flush-out prior to occupancy. This involves running the ventilation system with 100 percent outdoor air until a certain total volume of air has been supplied. If this process is to occur, the owner and contractor must be aware that it will delay occupancy significantly because the time required to complete it is roughly equivalent to 2 weeks after all interior finish work is complete. One hundred percent outdoor air may mean that heating or cooling costs are high during the flush-out, especially if the option to start occupancy before completion is taken. Recognizing the cost of a flush-out, LEED provides for indoor air quality testing in lieu of the flush-out, but the owner should understand that if the building doesn't pass the tests the credit can't be achieved without doing the flush-out after all.
Susan McClendon ([email protected]), an architect, is BSD's executive vice president and project director for BSD SpecLink®, BSD's specifications software product.
EPA and State Implementation Programs for VOC Reduction:
"The California Method:"
| Certification Programs Acceptable to CHPS and LEED:
Rating Systems:
EPA Indoor Air Quality References:
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