As a certified industrial hygienist practicing comprehensive health and safety at a major university, I have noted one area that consistently accounts for a majority of complaints and investigations: indoor air quality issues. Sure, requests flood our offices during the peak allergy seasons of spring and fall. But even in off seasons, we are constantly dealing with issues of poor or degraded indoor air quality. Why is this?
You have probably guessed the answer already: subpar indoor air quality (IAQ) management during new construction or renovation activities. Most off-season complaints originate from newly constructed or recently renovated work areas that are now newly occupied. However, with a little attention paid to building quality ventilation and heating, ventilating, and air conditioning (HVAC) systems, many of these problems can be avoided or eliminated.
IAQ , now more accurately referred to as indoor environmental quality (IEQ), has risen to the top of the list of worker complaints in the past decade. This is not surprising given that the U.S. Green Building Council (USGBC) and the U.S. Environmental Protection Agency now estimate that Americans spend an average of 90 percent of their time indoors, where potential contaminants and pollutant levels may be two to five times higher than outdoor levels.1 Add to this that an estimated 17 million Americans suffer from asthma and 40 million have allergies and you can easily see why indoor air quality is garnering so much attention.
IEQ involves many different parameters including temperature, relative humidity, odors, lighting, and even ergonomics, in addition to potential contaminants. The one contaminant receiving the most attention is mold; however, guidance on dealing with these issues will be a topic for future columns. Our focus here is how to minimize, or eliminate, IEQ problems associated with new construction to ensure that these areas are ready for occupation.
We begin with a comprehensive strategy for optimizing indoor environmental quality and minimizing potential problems from poor indoor air quality. Our IEQ management approach is based on the USGBC’s Leadership in Energy and Environmental Design (LEED) program,2 with a couple of important additions from the American Society of Heating, Refrigerating and Air-Conditioning Engineers’ (ASHRAE’s) Standard for Acceptable Indoor Air Quality, 62.1-2013.3 The LEED IEQ strategy addresses many areas, including meeting minimum indoor air quality performance standards, controlling environmental tobacco smoke, using low-emitting materials, increasing ventilation effectiveness, controlling chemical and pollutant sources, addressing thermal comfort, and optimizing the use of daylight, among others. ASHRAE’s standard concentrates on ventilation performance. We are going to focus on IAQ performance and assessment, which we refer to as IAQ commissioning—the testing of IAQ performance.
IEQ management plan/IAQ commissioning
Ideally, your construction IEQ management plan is a simple guidebook for ensuring that indoor air quality is acceptable following construction and prior to occupancy. We all know that construction activities produce a myriad of potential problems. In addition to the normal heavy particulate loads from constantly moving in and out, handling and installing building materials, preparing the site, and even cleaning and sweeping up, contaminants can also accumulate during the course of a project. These might include chemical pollutants or volatile organic compounds (VOCs) given off by building materials, as well as dust, pollens, and other particulates that enter from outside. The goal of the construction IEQ management plan is to reduce potential indoor air quality problems resulting from construction or renovation activities.
Under the LEED rating system, two options are provided— either a building flush out or IAQ commissioning (or testing). A brief description of a building flush out is provided; however, we believe you will agree with us and gravitate toward IAQ commissioning for your projects. We have modified the LEED testing to include a few parameters from ASHRAE that we feel are critical.
Building flush out
A building flush out is achieved by running the HVAC systems until a large amount of outside air has been delivered to the space. In following the LEED program for new construction or major renovations, the HVAC system is set for 100 percent outside air and operated continuously until 14,000 cubic feet (ft3) of outside air is delivered for each square foot (ft2) of new floor space. This can take a period of weeks, depending on HVAC system design, even when running 24/7. During flush out, the temperature must remain at least 60°F and the relative humidity cannot exceed 60 percent.
An alternate procedure is provided under LEED-New Construction that allows for quicker occupancy. This option permits the space to be occupied after flushing just 3,500 cubic feet of outside air per square foot of floor space, provided ventilation continues each day beginning three hours prior to occupancy and throughout normal occupancy hours, until the 14,000 ft3/ft2 is reached.
Because of the time and expense of conducting a building flush out, we prefer the second option of IAQ commissioning. Performing baseline indoor air quality testing demonstrates that certain common indicators do not exceed recommended maximum concentrations. Following our protocol, the indoor air is sampled for formaldehyde, total particulates, total VOCs, carbon dioxide, carbon monoxide, relative humidity and 4-phenylcyclohexene (4-PCH). Sampling for 4-PCH is required only if carpets and fabrics containing styrene butadiene rubber latex backing were installed as part of the base building systems.
In order to collect accurate and representative data, the testing must be conducted prior to occupancy and during normal occupancy hours. All HVAC systems must be operated at the normal daily settings (including the minimum outside airflow rate) during testing. All interior finishes must be installed. The number of sampling locations depends on the building size and the number of separate ventilation systems. Sampling should be done for each portion of the building served by a separate HVAC system and include at least one location for every 25,000 ft2. More samples or sampling locations may be required to assess the area with confidence. Finally, all samples should be collected from between three and six feet above the floor, the area representing the occupant breathing zone. The table below provides the maximum allowable concentrations for the recommended commissioning parameters.
Maximum Allowable Concentrations
|Formaldehyde||0.027 parts per million (ppm)||Off gases from many different building materials; severe irritant and sensitizer; probable carcinogen|
|Particulates (PM 10)||50 micrograms per cubic meter (ug/M3)||Introduced by many sources during construction; inhalation hazard; possible irritant|
|VOCs||500 ug/M3||Off gases from many different building materials; various effects resulting from irritation to the central nervous system (CNS)|
|Carbon Dioxide||< = ambient + 700 ppm||Ensure proper ventilation and percentage of outside air; performance indicator for HVAC|
|Carbon Monoxide||4.0 ppm||Produced by combustion sources; serious asphyxiate|
|Relative Humidity||<60%||Ensure proper HVAC performance, minimize mold growth|
|4-PCH||6.5 ug/M3||Off gases from specific materials; mucous membrane irritation, headaches, other possible CNS effects|
One downside to performing IAQ commissioning is the possibility of a parameter(s) exceeding the recommended limits. Should this occur, simply conduct additional flushing and then retest for only the specific contaminants found above the maximum levels.
1. LEED Reference Guide for Green Building Design and Construction. U.S. Green Building Council. Washington, DC. 2009. http://www.usgbc.org/resources/leed-reference-guide-green-building-design-and-construction
2. LEED 2009 for New Construction and Major Renovations Rating System. Version 2009. U.S. Green Building Council. Washington, DC. April 2013. http:// www.usgbc.org/resources/leed-new-construction-v2009-current-version
3. Ventilation for Acceptable Indoor Air Quality, American Society for Heating, Refrigerating and Air-Conditioning Engineers. Atlanta, GA. 2013. https:// www.ashrae.org/resources--publications/bookstore/standards-62-1--62-2
Indoor Air Quality. U.S. Environmental Protection Agency. Washington, DC. December 2008. http://www.epa.gov/iaq/
Indoor Environmental Quality. Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. Atlanta, GA. June 2013. http://www.cdc.gov/niosh/topics/indoorenv/
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