Today’s buildings are more tightly constructed than ever. This means that less airborne dirt and dust can infiltrate buildings from outside, but it also means that airborne particles generated in the space or brought into a building on clothing or by other means, or from construction or other materials installed in the building, cannot get out and are recirculated over and over again. These particles can cause unnecessary physical discomfort and illness.
The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Standard 62 “Ventilation for Acceptable Indoor Air Quality” specifies ventilation rate limits on formaldehyde, lead, and carbon monoxide and also provides procedures for achieving acceptable indoor air quality. While pure air is an ideal, the objective is to maintain concentrations of pollutants below threshold values. Ventilation rates are prescribed to achieve this.
Threats to indoor air quality include noxious gases, such as radon, carbon monoxide, propane, methane (natural gas), and formaldehyde—from natural sources, appliances, and man-made construction materials. Hospitals, labs, parking garages, gas stations, sewage treatment plants, airports, and factories may additionally have to control exposure to hydrogen, ammonia, and fluorocarbons (Freon).
Identifying such gases, their sources, and amounts enables professionals to determine an appropriate treatment. Monitoring CO2 can have an additional “green” benefit as some of the new energy management systems automatically adjust the temperature based on occupancy—as determined by CO2 level.
Off-Gassing of Construction Materials
Many forms of construction materials and products introduce contaminants into a facility, both initially and for many years after construction is completed. This is due to the off-gassing of contaminants over time until the product becomes stabilized, sometimes years later. Selecting natural carpeting, fabrics, flooring, and finish materials (including natural wall covering or, preferably, low- or no-VOC paints and wood floor finishes), and framing, sheathing, and cabinetry materials without harmful chemicals, is the green approach.
Materials constructed with potentially harmful chemicals, such as particleboard with formaldehyde resin, can sometimes be wrapped or sealed to reduce exposure (for example, millwork completely wrapped in laminate or coated with a nontoxic coating). Gypsum board and acoustic panels and ceiling tiles should also be investigated for toxic components before specifying. Natural floor materials, such as cork, bamboo, or linoleum are a better choice than vinyl, which contains potentially toxic chemicals.
Insulation is another potential source of indoor pollutants, from fibers and chemicals in materials such as cellulose, fiberglass, and mineral wool (which uses phenol formaldehyde binders), polyurethane spray foam, and polystyrene. Safer choices include Perlite, Icynene, and Air Krete, as well as scrap cotton. Formaldehyde-free fiberglass insulation is available from the major insulation manufacturers.
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