Volatile Organic Compounds
VOC's Are Listed as One of the Top Five Indoor Air Pollutants by the American Lung Association. VOC's are often found to play a major role in "Sick Building Syndrome" complaints.
What are VOC's
Volatile organic compounds (VOCs) are emitted
as gases from certain solids or liquids. VOCs include a variety of
chemicals, some of which may have short- and long-term adverse health
effects. Concentrations of many VOCs are consistently higher indoors (up to
ten times higher) than outdoors. VOCs are emitted by a wide array
of products numbering in the thousands. Examples include: paints and
lacquers, paint strippers, cleaning supplies, pesticides, building materials
and furnishings, office equipment such as copiers and printers, correction
fluids and carbonless copy paper, graphics and craft materials including
glues and adhesives, permanent markers, and photographic solutions.
According to the American Lung Association, the top five indoor air pollutants include:
In evaluating indoor air quality complaints, mistakes are often made in the techniques or equipment chosen to perform the task. Many in our industry use carbon dioxide (CO2) measurements as the sole indication of good indoor air quality. This is often the case during building commissioning. CO2 measurements and datalogging can be an indicator of poor ventilation in a building. However, CO2 is not an indicator of VOC levels. VOC levels are often overlooked by making this assumption in buildings where sick building syndrome (SBS) complaints later appear. CO2 levels do not correlate with Total Volatile Organic Compounds (tVOC's) in buildings, nor do high VOC levels indicate poor ventilation.
Above are two tools used during an indoor air quality complaint investigation. On the left is Casella Microdust Pro which measures respirable dust (particulate) levels and on the right is a Telaire 7001 with Hobo H8 datalogger for measuring CO2 levels.
To Volatile Organic Compounds TVOC
Normal Measurement Equipment
The canister is placed at a suitable
location and actively collect the indoor air for 4, 6, 8 or more hours, then it is
returned to the laboratory for further analysis.
Surrogate Measurement Equipment
The TVOC is measured with RAE ppbRAE
(shown above) using
photo-ionization technique and the detectable range is from 0 - 999 ppb. For
30-minutes short-term measurement, the measured data is recorded on-site
after completion of the measurement.
There are several options available for measuring VOC's. All have their pro's and con's. Although we may use any or all techniques during an assessment, we most often choose the ppbRAE. Some of the options available include:
The image on the left is a summa can used for collecting VOC air samples. C.L.I. Group, LLC typically would use the ppbRAE PID to evaluate the environment immediately, followed by adsorbant or summa can testing if deemed necessary for tVOC identification.
In many cases, we can use the ppbRAE during our investigation to track the source(s) of odors. After locating the suspect items, we may be able to find information on the product (e.g. paint). Using correction factors (CF) after we have identified the target, a PID can quickly and accurately measure the level of paint fumes. These levels can then be compared to accepted standards to see if levels are safe. This allows for an immediate response to complaints and reduces the liabilities of the building owner while protecting the health of the occupants.
In addition to measuring VOC levels, the ppbRAE can measure mVOC's (Microbial Volatile Organic Compounds) and is a helpful tool when microbial contamination is suspected but may be hidden in walls, etc.
Our abilities to measure ventilation, building parameters (CO2, CO, %RH, Temperatures and Dew-Points) along with using state of the art photo-ionization detector (ppbRAE), real-time IAQ monitors and additional equipment allows us to provide immediate answers to many air quality problems so that immediate decisions can be made.
General Guidelines of PID Use in IAQ
Global consensus has resulted in the emergence of preliminary guidelines for tVOC standards for IAQ (Australian NHMRC, 1993; Finnish Society of IAQ, 1995; Seifert, 1999; Hong Kong EPA, 1999; Japan MoH, 2000). Depending on location (home, school, etc.), recommended levels range from 200 to 1300 ug/m3 or about 50 to 325 ppb (Toluene units) or approximately 100 to 650 ppb isobutylene units. By all accounts, the IAQ tVOC threshold for normal environments should not exceed 500 ppb (0.5 ppm) toluene units, which is equivalent to 1000 ppb (1 ppm) isobutylene units. Field experience suggests the following guide for the use of PIDs to assess indoor environments:
Source: Rae Systems, Inc. Application Note-212
Further VOC information
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