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CONSTRUCTION INNOVATION, Fall 2000
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Fire researchers use new tool for hazard assessment
Fire researchers at IRC are using an FTIR (Fourier Transform Infrared) spectrometer to obtain data on smoke components for use in hazard assessment. FTIR has become an important tool in the IRC arsenal for understanding the impact of different materials in fires on building occupants.
Traditionally, smoke gas analysis has focused on the measurement of oxygen, carbon dioxide (CO2) and carbon monoxide (CO). By measuring carbon monoxide, the quantity of the main toxic component produced in a fire could be determined and used along with smoke obscuration measurements to make assessments of occupants' ability to move through a space and maintain mobility for purposes of evacuation. Other combustion by-products, if measured at all, were determined using standard analytical chemistry techniques, including gas chromatrography and mass spectrometry.
These traditional techniques have a number of limitations - in particular, they are time consuming and do not allow for the continuous monitoring of selected fire gas components. Also, many fire gases are very reactive so that they break down or react in the storage system, making it difficult to obtain representative samples and to have confidence in the results.
Today, with the increasing use of synthetic polymers, composites and flame-retardants in building materials and consumer goods, there is a greater need to be able to measure a broad range of combustion by-products, in order to assess any hazards they might pose. The FTIR spectrometric technique has definite advantages over previous methods, as it is able to provide continuous monitoring of secondary gases such as hydrogen cyanide, hydrogen halides, methane, ethylene and acetylene, as well as CO and CO2, which is not possible with more traditional methods.
USING THE FTIR TECHNIQUE TO ANALYZE SMOKE FROM A BURNING MATTRESS
In this technique, an infrared light source shines through a gas sample and the absorption of infrared light over a range of wavelengths is determined. (Each molecule has specific wavelengths at which it will absorb the infrared light.) Calibration procedures are used to determine the concentration of selected components.
IRC has successfully linked the FTIR concept to its full-scale fire-testing program, which in many cases simulates real-fire scenarios in residential, retail and office environments and includes tests with clothing, toys, furniture such as sofas and beds, and computer cable. Specifically, carbon monoxide and carbon dioxide concentrations measured using the FTIR technique are comparable to those measured with traditional gas analyzers in full-scale fire tests. As well, the FTIR data yielded additional information on many other combustion by-products, providing further insight into the dynamics of fires.
Specific questions can be directed to Dr. Malgosia Kanabus-Kaminska at (613) 993-6302, fax (613) 954-0483, or e-mail malgosia.kanabus-kaminska@nrc-cnrc.gc.ca.
