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(a) Blast-Cleaning Enclosures.
(1) Blast-cleaning enclosures shall be exhaust ventilated in such a way that a continuous inward flow of air will be maintained at all openings in the enclosure during blasting operations. It is recommended that the following minimum ventilation rates as prescribed in the appendix of ANSI Z9.4-1968, Ventilation and Safe Practices of Abrasive Blasting Operations be used:
(A) Blast-cleaning cabinet, 500 feet per minute calculated on the free opening without the curtains.
(B) Rotary blast-cleaning tables, 200 feet per minute calculated on the free opening without curtains.
(C) Blast-cleaning rooms, 300 feet per minute at air inlets.
(2) In blasting enclosures, safety glass protected by screening or equivalent shall be used in observation windows where hard abrasives are used. All access openings in blast-cleaning enclosures shall be designed, inspected regularly, and maintained when needed, in order to prevent escape of dust. Blast-cleaning room doors shall be flanged and tight when closed and shall be operable from both inside and outside.
(3) In installations when the abrasive is recirculated, an abrasive separator shall be provided for the removal of fines from the spent abrasive.
(4) Abrasive blasting enclosures shall not be opened until visible airborne dust has been removed by the exhaust system.
(b) Personal Protective Equipment.
(1) Abrasive blasting or equivalent respirators shall be worn by employees under the following conditions:
(A) Inside blasting rooms during operations.
(B) During continuous blasting operations where concentrations of dust dispersed by abrasive blasting operations may exceed limits prescribed in Section 5155.
(C) During continuous blasting operations where silica sand is used as the blasting abrasive or when toxic materials are blasted. Dust-filter respirators may be used for periods up to two hours per shift, providing the concentrations of silica dust do not exceed ten times the time-weighted, eight-hour exposure limit as specified in Section 5155. Use of respiratory protective equipment is prescribed in Section 5144.
(2) Equipment for protection of the eyes and face shall be worn by the operator when the respirator design does not provide such protection and by any other personnel working in the vicinity of abrasive blasting operations.
(c) Organic Abrasives. Organic abrasives which are combustible shall be used only in automatic systems. Where flammable or explosive dust mixtures may be present, the construction of the equipment, including the exhaust system and all electric wiring, shall conform to the requirements of Section 5174 and the Electrical Safety Orders, Title 8, California Administrative Code. (Title 24, T8-5151(a), (c))
NOTE: Authority cited: Section 142.3, Labor Code.
1. New section filed 7-18-75; effective thirtieth day thereafter (Register 75, No. 29).
2. Amendments filed 7-16-76; effective thirtieth day thereafter (Register 76, No. 29).