Silica Comparison: Wet vs. Dry vs. Vapour Blasting

 Media: Medium recycled crushed glass

 Blast Hose: 15 m (50 ft) x 38.1 mm (1.25 in) ID

 Nozzle: #8 High Performance

 Compressor: Doosan 425 CFM

 Substrate: 1.22 m x 1.22 m (4 ft x 4 ft) Concrete Slab

 Blasting Time per Test: 25 – 28 minutes
 

Graco retained a third party to perform an Industrial Hygiene Survey in order to evaluate potential exposures to respirable airborne dust and respirable silica during three separate blasting operations. Blasting parameters were kept constant for the three scenarios with the exception of the blasting equipment used and the usage of water. Blasting was performed on a 1.22 m x 1.22 m (4 ft x 4 ft) slab of concrete using medium crushed glass abrasive.

Occupational exposures to airborne contaminants are evaluated by comparing them to Permissible Exposure Limits (PELs) and Short-Term Exposure Limits (STELs) established by OSHA. PELs are time-weighted average (TWA) concentrations for a normal 8-hour workday or a 40-hour work week. STELs are 15-minute TWA concentrations that shall not be exceeded any time during the workday.