Carbon as Diesel Particulate
What is Diesel Particulate Matter?
Diesel particulate matter (DPM) is a byproduct of combustion in diesel powered engines. It can be seen as black soot emitted from the exhaust pipes of diesel trucks and other heavy equipment. Diesel exhaust consists of thousands of different chemicals,many of which are in the form of respirable particulate matter. The particles enter the lungs and become trapped there. They can exacerbate respiratory problems such as asthma and bronchitis, and can cause long-term lung damage, cancer, and early death.
In an effort to reduce the amount of air pollution resulting from diesel combustion, the USEPA is currently working toward tougher emissions standards in trucks, buses and heavy equipment. Organizations such as the Mine Safety and Health Administration (MSHA) and American Conference of Governmental Industrial Hygienists (ACGIH) are either implementing or recommending tougher limits for worker exposure to diesel particulate matter.
Carbon as a Surrogate for Diesel Particulate Matter
Diesel exhaust consists of an elemental carbon core, and attached to this core can be thousands of different compounds. The compounds present in the exhaust can vary with the type of engine used, the diesel gas source, and environmental conditions. As a result of this variability, it is impossible to use any one method of analysis to measure whole diesel exhaust.However, since elemental carbon (EC) is known to consistently represent 60-70% of diesel particulate matter, it is being used as a surrogate to assess for exposure to diesel exhaust. Some organizations, for example, MSHA,are using total carbon (organic plus elemental carbon combined) to assess diesel exhaust exposure.
Several different collection devices are available. The type of cassette chosen will depend on the environment in which the samples are to be collected.
Cassette with Precision-Jeweled Impactor – produced by SKC, Inc. and available from Galson Laboratories. It is designed for metal/non-metal mines and is a must for MSHA compliance. It is designed to exclude dusts greater than 1 micron. Since diesel exhaust is 80-95% submicron, this cassette allows for removal of larger dusts such as carbonaceous minerals,which may interfere with the analysis while still capturing the smaller diesel particulates. The cassette contains a heat-treated quartz filter and is assembled in a clean room.A second filter is also provided in the cassette,which may be used as a blank. A cyclone may also be used to eliminate larger dusts from the cassette to help prevent the impactor from becoming clogged.
Conventional Cassettes – standard 37- mm cassettes with heat-treated quartz filter and cellulose backup pad, also manufactured by SKC Inc. and provided by Galson Laboratories. To be used in environments where non-diesel respirable particulate matter is at lower concentrations, and therefore, less likely to pose an interference. A cyclone is recommended. Do not use if MSHA compliance is required.
How does Galson Laboratories analyze for Carbon as Diesel Particulate?
Galson Laboratories follows NIOSH method 5040 for Elemental Carbon (Diesel Particulate). This method employs the evolved gas analysis (EGA) technique by using a thermal-optical analyzer manufactured by Sunset Laboratory Inc. Results for elemental, organic, and total carbon are reported.