Crystalline silica is a hazard before, during and after blasting activities. Abrasive blasters, pot tenders, cleanup crews and adjacent workers can be affected. Silica dust is created at any point where abrasives are transferred to trucks or machines, whether by hand or shovel. Dry blasting generates huge clouds of silica containing dust. Even if a wet blasting method is selected silica that is allowed to migrate into other work areas, by either wind or water, will eventually dry to become an airborne contaminant.
OSHA’s new Final Rule for Crystalline Silica underscores the theme of containment and control. The rule increases protections for employees exposed to silica in the workplace and imposes new and substantial obligations on employers - such as a requirement that medical surveillance be made available to employees required to wear a respirator for 30 or more days per year, or who are exposed to silica above the PEL for 30 or more days per year.
The most significant change is the revised permissible exposure limit (PEL). The prior PELs for silica were 100 micrograms of silica per cubic meter of air (µg/m3) for general industry and 250 µg/m3 for construction and shipyards. OSHA set a new silica PEL at 50 µg/m3 (8-hr time-weighted average [TWA]) for all industries. The new rule is triggered by an Action Level above 25 µg/m3.
The new regulations establish a hierarchy of controls that employers must implement to reduce and maintain exposure to silica to levels below the PEL, emphasizing the primary means of reducing exposure though work practices by mandating that employers develop a written exposure control plan (ECP). For example, dry sweeping, blowers, and dry brushing are prohibited. Waste collection for wet methods must prevent dust from remaining in the work environment to eventually dry and disperse into nearby areas.
The ECP describes methods used to identify and control workplace exposures. Employers assess the exposure of employees who may reasonably be expected to be exposed to silica at or above the 25 µg/m3 action level and note their methods to ensure compliance with the PEL. The ECP should demonstrate to OSHA employer commitment and due diligence in efforts to select the most effective control technologies available, and ensure best practices are followed at worksites.
One obvious means to do so would be to switch to wet abrasive vapor blast methods. Vapor blasting consumes only a fraction of the grit used in dry abrasive blasting. Lower grit media consumption means lower total dust and waste generation, thus ensuring significantly reduced airborne concentrations and assured compliance.
CleanerBlast machines are a great vapor blasting option. Each unit uses up to 90% less grit and generates up to 91.7% less dust & waste. Small volume vapor blasting pods (suitable to prepare or clean approximately the SAME sq. ft/hr. as comparable dry blast machines) are reloaded half, or less, often (depending on grit size),thus reducing exposure for grit handlers as well. Because spent grit may be directly collected in a blast bag or using a HEPA filtered wet vacuum, cleanup crew exposure is also significantly reduced.