Keeping tabs on indoor air quality
Problems developed from energy conservation measures adopted in the late 1970s that limited functioning windows and introduction of outside air into buildings. The resultant “tight” buildings and 100 percent recirculating heating, ventilating, and air conditioning (HVAC) systems produced myriad problems for building occupants and owners alike. What began as a few cases of tight building syndrome exploded into high-profile cases of multiple chemical sensitivity and indoor mold contamination, and IAQ issues were born.
Today, we are in much better shape thanks to the efforts of the Environmental Protection Agency (EPA); Occupational Safety and Health Administration (OSHA); American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE); and the US Green Building Council (USGBC). Both the EPA and OSHA have extensive information and guidance on their respective websites.1,2 You can learn as much as you want to know about indoor air quality, building systems, preventing problems, and troubleshooting with the comprehensive materials developed by these government agencies. And the good news is, it is free. Nongovernmental organizations such as ASHRAE and USGBC have also advanced the science of indoor air quality. ASHRAE’s ventilation guide is considered by many to be the IAQ designer’s bible, providing very important information on fresh outside air quantities.3 USGBC’s Leadership in Energy and Environmental Design (LEED) program presents cuttingedge guidance for designing and building the new generation of green buildings, focusing on occupant health and indoor air quality.4
However, even with this wealth of information and today’s sophisticated HVAC systems, indoor air quality issues arise due to many different and prevalent reasons (e.g., a preventive maintenance was missed, a belt broke on a crucial exhaust fan, a suite was just renovated with new furnishings and floor coverings, or a delivery truck sat parked in front of the outside air intake for a few hours). We have run into all these issues and spent valuable time running down the causes and correcting the problems. Some transgressions are unforeseeable and unavoidable, but many can be headed off or even prevented with minimal effort focused on routine checking of the facility’s indoor air quality.
How do we check our IAQ?
Digging through the massive volumes of indoor air quality information is daunting for most of us and too time consuming. Many people often deal with situations only when they become a crisis. Then they are scrambling to fix the problem or call in experts. But having dealt with IAQ issues for the past couple of decades and pored over the guidance documents, we have developed a tool—an air testing protocol that may help prevent many of the common indoor air quality issues.
This air testing protocol is based on Environmental Protection Agency IAQ studies and USGBC’s LEED indoor air quality commissioning requirements. It consists of a complete facility (or area of concern) survey for specific parameters and contaminants and is performed with portable instruments so data is available immediately. It is quick, simple, and inexpensive, even if consultants are hired to perform the work (an alternative is to rent the instruments and have in-house staff take the measurements). Best of all, the data is directly compared to existing OSHA, EPA, ASHRAE and LEED standards or recommended guidance levels and related to occupational health conditions.
Base IAQ assessment protocol
Begin the indoor air quality survey by taking measurements of the classic four parameters: temperature, relative humidity, carbon dioxide, and carbon monoxide. This is most easily done using a modern handheld IAQ meter, such as the TSI Q-Trak™ or equivalent, which can measure these four parameters at once. Temperature, relative humidity, and carbon dioxide are important indicators of HVAC system performance as well as occupant comfort. ASHRAE standard 62.1-2010 provides excellent guidance on these criteria. If problems pop up with these indicators, it could mean the system is out of balance or the percentage of outside air is insufficient. Carbon dioxide is also dependent on occupant loading and tends to increase during the workday. If “hot spots” of accumulation are noted, first verify the proper amount of outside air, then check the supply flows for adequate distribution in the area. ASHRAE recommends that carbon dioxide levels be kept below the ambient level plus 700 ppm.3 The theoretical amount of carbon dioxide in outdoor air is around 350 ppm.
Carbon monoxide is introduced from combustion sources. The OSHA-permissible exposure limit is 50 ppm, a level you should never come close to inside a typical building or research laboratory facility. The EPA and LEED recommend an upper limit of 9 ppm or 2 ppm above the ambient level, whichever is lowest. Our experience indicates that if you see levels of carbon monoxide above a few parts per million, you should seek out the source and eliminate it.
The next step is to survey dust levels. The amount of particulates in the air provides a good indication of HVAC system performance and filter condition when compared to outdoor levels.
It also provides valuable information on activity levels— especially in research facilities, where the potential for airborne contaminants is a concern. Measuring dust is a little trickier than measuring the classic comfort parameters, but state-of-the-art instrumentation such as the TSI Dust-Trak™, or equivalent, makes it easier. Dust is usually measured in milligrams per cubic meter of air (mg/M3) and reported for a specific particle size: median diameter of 10 microns or less and designated PM10. As for carbon dioxide, levels are compared to both OSHApermissible exposure limits and LEED-recommended criteria. And when dealing with indoor air quality, never approach the OSHA PEL, which is 10 mg/M3. The amount recommended by LEED standards is 0.05 mg/ M3. Typical ambient levels with normal activity are about half the LEED standard, and indoor office spaces will usually be in the microgram per cubic meter range.
The next step in our base IAQ protocol is to evaluate the levels of volatile organic compounds (VOC). This can also be performed using handheld instrumentation such as our favorite, the RAE Systems ppbRAE™.This nondiscriminating photo-ionization detector measures hundreds of common VOCs and provides a “total” VOC reading in either parts per million or parts per billion in air. While it is true that, in typical office environments, these readings can be the result of perfumes, colognes, and air fresheners, these sources pale when compared to common commercial sources such as paints, adhesives, thinners, strippers, and lubricants. And in a research setting, the multitude of chemicals in use must be considered. So VOC levels are a very important piece of the puzzle because there are many potential sources and most have serious health and safety consequences as well. The recommended level under LEED is less than 500 ug/M3. For comparison, we typically see levels between 200 and 300 even in hospital and laboratory buildings.
One final contaminate to consider is formaldehyde. If your facility has undergone recent new construction or renovation, testing for this contaminate is worthwhile as formaldehyde is contained in many urea resins, insulation, plywood, particle board, adhesives, and textiles. In addition, given its use as a preservative and sterilizer, research labs should definitely include this parameter. However, real-time measurements necessitate the use of portable infrared spectrophotometers, which are expensive to buy or rent and take some expertise to operate correctly. We would recommend using low-flow sample pumps with appropriate media and having the analyses done by an accredited laboratory. For reference, the OSHA PEL is only 0.75 ppm and the LEED standard for indoor air quality is 27 ppb.
Now you have the Safety Guys’ protocol for regular IAQ assessment. We suggest performing this screening at least annually and more often if your facility has serious issues or lots of employee complaints. By surveying your indoor air quality regularly, you can find and prevent many common problems before they become serious. The Safety Guys welcome your comments and questions. Until next time, remember: “Safety First!”
1. Indoor Air Quality, US Environmental Protection Agency. Washington, D.C. October 2010. http://www.epa.gov/iaq/
2. Indoor Air Quality, Occupational Safety and Health Administration. Washington, D.C. http://www.osha.gov/SLTC/indoorairquality/index.html
3. Ventilation for Acceptable Indoor Air Quality. American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) Standard 62.1-2010. Atlanta, GA. http://www.techstreet.com/standards/ASHRAE/62_1_2010?product_id=1720986
4. United States Green Building Council, LEED Resources. Washington, D.C., 2011. http://www.usgbc.org/DisplayPage.aspx?CMSPageID=75&
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