Part I – Physical Reasons Why Engineering Controls Cannot Provide 100% Containment of all Crystalline Silica
- Respirable Crystalline Silica (RCS) is nearly as light as air, invisible, and migrates with the prevailing air currents both inside and outside any areas of containment.
- RCS has a very slow settling rate even in a controlled environment. Recent studies show it takes as long as 57 minutes for RCS to settle inside an enclosed chamber after agitation.
- There are approximately 35.3 million RCS particles per cubic meter of air at current OSHA Permissible Exposure Limit of 0.1 mg/m3.
- The currently available engineering controls are not manufactured to be “air tight” and create a false containment condition.
- Several engineering controls, such as shrouds, vacuum systems, exhaust plenums, are manufactured as sheet metal retrofits.
- The nature of retrofitting, and the standard tolerances used in sheet metal fabrication, create multiple gaps/holes/crevices between the pieces of equipment being retrofitted.
- The process of welding components together is not usually viable due to the mobility requirements of the industry. Most engineering controls need to be designed for removal and relocation.
- The majority of these retrofits systems do not utilize proper gasketing techniques and/or clamping components necessary to create an air tight condition.
- Most sheet metal retrofits use the weight of the system and/or standard bolt/nut fastening to join the equipment together. This leaves hundreds to gaps in the perimeter of the equipment through which RCS will always escape.
- We have also seen companies promote a basic system of “Tarps and Magnets” to contain certain areas of sand moving equipment.