Engineering & Mining Journal

JUN 2014

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In the world of worker exposure measure- ment, the gold standard is a wearable instrument that monitors in real time. For this purpose, the National Institute for Occupational Safety and Health (NIOSH) has developed a real-time diesel particu- late matter (DPM) monitor. This monitor provides miners with timely information to identify the major factors contributing to overexposures, which can be helpful in reducing DPM exposures by allowing con- trol interventions to be deployed immedi- ately. This article evaluates the accuracy of this monitor (the FLIR Airtec) and reveals how it can be used as a tool for assessing and controlling DPM exposures. Background on Measuring DPM Exposure Exposure to DPM is a health concern for miners because it has been classified as a carcinogenic to humans by the International Agency for Research on Cancer (IARC) (IARC 2012). Since underground miners work alongside diesel equipment in a con- fined environment, they can be exposed to elevated concentrations of DPM. Therefore, the Mine Safety and Health Administration (MSHA) promulgated a rule to limit DPM exposures of metal/nonmetal underground miners (MSHA 2006). The standard method for determining DPM exposures is to collect the particulate onto a filter for an entire shift. The sample is then sent to a laboratory to be analyzed for elemental carbon (EC) and total carbon (TC) using NIOSH method 5040. Although an accurate method for determining DPM exposures, NIOSH method 5040 only pro- vides the average concentration over an entire working shift and can take weeks to obtain results. While this approach does determine that an overexposure has occurred, it fails to provide critical infor- mation about cause or prevention. Conversely, real-time measurement would provide miners with timely information to identify the major factors contributing to overexposures. This information would allow control interventions to be deployed immedi- ately. To this end, NIOSH developed an instrument to measure real-time EC exposure via laser extinction (Noll et al. 2013). EC was chosen as the analyte because it makes up a major portion of DPM, is not prone to inter- ferences, and is one of the surrogates used by MSHA for compliance sampling. Filter- based laser extinction (which employs absorption and scattering) was determined to be a feasible method because EC concentra- tions can easily be correlated to laser absorp- tion. In addition, this simple technique can be adapted into a small instrument. This instrument, the FLIR Airtec (see Figure 1), is now commercially available. The Airtec has been shown to be accu- rate in both the laboratory and field. It was found to be within 10% of the standard method in the laboratory (Noll et al. 2013) and was equivalent to the standard method when measured side-by-side in extensive field samples (Noll and Janisko 2013). The only observed influences from other aerosols on the Airtec reading can occur when a miner is smoking inside a cab, which can be avoided if the miner simply does not smoke inside the cab during sampling. Using Real-time Measurement for Administrative Controls To protect blasters, surveyors and other miners who must work outside of cabs, some mines are implementing administra- tive controls to reduce DPM exposures. These administrative controls include oper- ating high-emitting vehicles on different shifts or downstream from miners who work outside of enclosed cabs, limiting the number of vehicles in an area, and spot checking areas before miners enter. The Airtec provides a tool to help admin- ister these controls more efficiently. It serves as a measurement tool for spot checking, which cannot be performed without a real- time monitor. It also helps ensure that DPM overexposures do not occur—even for administrative controls that do not necessar- ily require real-time monitoring such as lim- iting the number of vehicles in an area or operating some vehicles only downstream of blasters. When a mine attempts to imple- ment these types of administrative controls without the Airtec, the concentration of DPM can be elevated for some time before it is noticed that too many vehicles are oper- ating upstream of the miners of concern. But with the Airtec, the DPM concentration can be continuously monitored. Blasters, surveyors or other designated miners can then know quickly when elevated DPM con- centrations exist in certain areas. Evaluating Enclosed Cabs and Control Rooms with Real-time DPM Measurements The real-time feature of the Airtec allows for the evaluation of an enclosed cab sys- tem without the influence of confounders such as opening and closing doors and win- dows. Enclosed cabs can be very effective 78 E&MJ; • JUNE 2014 www.e-mj.com D P M M O N I T O R I N G Real-time DPM Monitoring NIOSH develops a new tool for assessing and controlling exposure By James Noll, Andy Cecala, John Organiscak and Sam Janisko Figure 1—The FLIR Airtec: a real-time DPM monitor. EMJ_pg78-81_EMJ_pg78-81 6/3/14 3:23 PM Page 78

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