What is Fugitive Dust?
The term fugitive dust refers to particulate that is lifted into the air either by man-made or natural activities in large open areas.
Fugitive dust is typically the result from mining activities such as the physical movement of soil, vehicles traveling over unpaved surfaces, heavy equipment operation, blasting, and wind, which can erode mine tailings piles to create potentially contaminated fugitive dust. Equipment moving on unpaved roads or parched soil, and the storage and movement of aggregate piles also produce fugitive dust, more commonly known as dust bowl conditions. This release into the atmosphere does not happen in a controlled manner nor does it necessarily originate from a known source point. Particulate resulting from combustion (motor vehicles and other internal combustion engines) and transformation operations such as soldering, brazing or welding are typically excluded from the general definition of fugitive dust.
The health impacts on personnel in contact with the fugitive dust conditions can be severe. If the particles carry chemicals such as silica from mining operations, the lungs can be permanently damaged. Furthermore, maintaining exposure limits is critical to achieving compliance.
How Much Is Too Much?
While various environmental regulatory groups establish definitions for source of dust and maximum exposure levels, it is difficult to know if your dust control plan is effective. The Clean Air Act (CAA) of 1970 established National Ambient Air Quality Standard (NAAQS) for a number of hazardous pollutants.
One of those hazardous pollutants identified in this overarching document was particulate matter (PM). Fugitive dust is not a direct part of the NAAQS, however these emissions do contribute heavily to the overall particulate measurement and the exposure limits. Emissions are usually controlled by the local regulatory authority such as state EPA or Department of Environmental Quality Engineering, air quality management districts, air resource boards or special program agencies.
Permissible levels of exposure and enforcement vary widely. Most regions have established exposure limits on projects that typically result in high level of particulate generation and the exposure limits are written into the operating permit. The operating permits vary by the type of projects, such as construction, remediation and demolition, and dust exposure is often permitted at a higher level than the NAAQS due to the nature of the work. Once the limit is approached, control of the dust emissions can be reached through a number of local containment efforts including water sprays and cover materials to reduce the airborne dust while active work is being performed. As the project approaches completion, more permanent measures such as landscaping and/or paving can be employed to reduce emission to normal ambient levels.
What’s the Solution to Fugitive Dust at the Mine Site?
Fugitive dust exposure levels require continuous, real-time monitoring at mine sites because conditions can change quickly as new sections are opened and dirt moving operations are in place. This requires instrumentation that provides a quick response, is dependable, can be quickly deployed or relocated and has the performance capabilities stated in the governing guidelines or within the site permit.
A light scattering device (nephelometer) provides the real-time measurements required to take immediate corrective actions for the excursion above the exposure limit. Since the concentrations will likely vary depending on the activities being performed, a wide measurement range is usually required to be able to capture heavy concentrations. In addition, constant high concentrations can result in very high dust loading on filter-based nephelometers, which can cause the particulate sizing controls (cyclone or impactors) to not perform properly due to reduce flow. A dust monitor with volumetric flow control is critical to assure the proper flow is maintained.
Lastly, as work areas of this type are usually very fluid with respect to specific areas being monitored, an instrument that provides quick set up and the ability to withstand the normal monitoring conditions (hear, rain, wind) should be selected.
Read this application note to learn more about the issue of fugitive dust and the tools and technologies available to monitor it.