Abstract
Since 1999, the CWP level among miners with 25 years or more experience, for instance, has risen from slightly more than 4% to 9% (See Figure 1). While it is obviously necessary to protect all miners' lungs, there is now a technology to improve the chances that new miners' lungs will be protected from the day they begin work. A new personal dust monitor (PDM) can help miners to be better aware of the respirable dust levels in their environment. The PDM differs significantly from the present sampling system with its gravimetric pump. Today's miners may not have access to dust exposure measurements until several days after the sample is taken. Also, the current sampling program only measures dust concentrations in the environment of an occupation being sampled. It does not necessarily reflect an individual miner's dust exposure. With the PDM, miners will be provided with near real time dust exposures during their work shift, enabling individuals and management to be more proactive in preventing overexposures. The PDM was previously field tested at 10 mines; it was found to be durable and reliable. Test results demonstrated that the PDM could measure respirable dust levels as accurately as the current sampler. To fulfill its intended purpose, however, it must be used correctly. Therefore a project was developed that would systematically document how workers react to wearing the PDM and evaluate how it is used on the job. To make the unit more convenient for miners to wear it is combined with a cap lamp battery into a single piece. There is no extra hardware to carry around. The PDM has several components that are shown in Figure 2. The inlet of the sampler is built into the cap lamp itself. Air is drawn into the inlet at a flow rate of 2.2 liters a minute (l/min). The air travels through a rubber tube that runs alongside the lamp cord. Internal electronics calculate respective concentrations based on flow rates and times. These data are shown on a display screen on top of the battery housing. At the same time, concentration data are recorded to internal memory so that it can later be downloaded to a computer. In normal operation, the PDM will be programmed to automatically start, stop, and record an entire shift of data. No person can alter the programmed functioning of the PDM until it is reconnected with a computer by a responsible person in charge of the mine's sampling. There are parts of the PDM, however, with which miners may interact. These include the two switches and display on top of the unit. The switches allow workers to toggle through screens that provide feedback on the concentration of respirable dust to which they are being exposed. For instance, one screen provides the mass concentration value for the past 30 minutes, the average mass concentration from the beginning of the shift, and the projected mass concentration for the entire shift. Another screen displays a bar chart showing concentrations in milligrams per cubic meter (mg/m3) in 30 minute averages. A new bar is added to this chart every 30 minutes. A miner's interactions with the PDM display buttons during his or her work will have no effect on the ability of the instrument to measure and record exposure data. The miner cannot accidentally alter the preprogrammed functioning of the PDM.
