Engineering Controls for Silica Art Wickman, CIH Georgia Tech Safety & Health Consultation Program

Control Options 1. Wet Methods 2. Ventilated Tools 3. Abrasive Blasting Controls: Alternate Media Alternate Methods

Engineering Controls: 1. Wet Methods Water suppression of dust Very effective method Requires planning for supply of water and clean up

Note: Safety Glasses Required

Wet Methods: Portable Saw

Block Cutting: Dry Monitoring Data: 8 X OSHA PEL Time Weighted Average (TWA)

Block Cutting--Dry

Wet Methods: Block Cutting

Wet Methods: Requires Pre-planning

Wet Methods: Joint Cutting

Wet Methods: Jack hammer, chipping hammer, etc.

Double click photo for demo

Wet Methods: Spray Systems for Bulk Materials

Engineering Controls 2. Ventilation Portable tools with dust exhaust: Surface Grinders Disc Grinders (tuck pointing) Crack chaser Scarifier Descaler Power chipping tools Retrofit Dust hoods (Dust Muzzle Video)

Tuckpointing Note: Fall Protection Required

Control by Ventilation: Tuckpointing

Control by Ventilation: Slab Cutting Note: Safety Glasses Required

Control by Ventilation: Hand tools

3. Abrasive Blasting

Engineering Controls: 3. Substitute Abrasives Coal slag (Low silica content, but may contain trace metals including arsenic) Steel grit & steel shot Aluminum oxide Sodium Bicarbonate (baking soda) Dust Suppressed Sand Frozen CO2 Ag. Prod. (walnut shells, corn cobs)

Substitute Abrasives: Blast and Recovery Systems Permits multiple cycles of abrasive Reduces cost of more expensive abrasives Reduces fugitive emissions to Environment

Alternate Abrasive Methods: Wet Blasting Similar to conventional air blasting Water injected into air/abrasive stream, or Water pressurized with abrasive Work rate <50% of dry abrasive Abrasive consumption <20% of dry Better visibility, lower waste volume

Alternative Blast Method: Enclosure

Alternate Abrasive Methods: Water Jetting 1. High Pressure 10,000 – 25,000 psi Removes most paint, rust, mill scale, chemical contaminants 2. Ultra High Pressure >25,000 psi Removes all coatings Processes can use vacuum shroud to retain/recycle water

Alternate Abrasive Methods: Sponge Jet Blasting Dry method, suppressed dust, minimal containment required Light to heavy abrasion Less aggressive cleaning Eliminates the hazards of high pressure blasting