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Subchapter 4. Construction Safety Orders
Article 4. Dusts, Fumes, Mists, Vapors, and Gases
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§1530. General Requirements of Mechanical Ventilation Systems.

Guide to Respiratory Protection at Work

(a) Design and Operation.

(1) When local exhaust ventilation is used, the system (including exhaust fans, jets, ducts, hoods, separators, and all necessary appurtenances) shall be designed, constructed, installed, inspected, tested, maintained, and operated so as to ensure the required protection by maintaining a volume and velocity of exhaust air sufficient to gather dusts, fumes, mists, vapors, or gases from the equipment or processes, and to convey them to suitable points of safe disposal, thereby preventing their dispersion in harmful quantities into the atmosphere of work rooms or other places where persons are employed.

(2) When general mechanical ventilation is used, the volume and distribution of air shall be sufficient to dilute airborne contaminant concentrations in employees' breathing zones to safe levels.

(b) Duration of Operations. The exhaust system shall be in operation continually during all operations for which it is designed. The system shall continue to operate some time after the cessation of said operations, the length of time to depend upon the individual circumstances and effectiveness of the ventilation system.

(c) Disposal of Exhaust Materials.

(1) The air outlet from every dust separator/collector and the dusts, fumes, mists, vapors or gases collected by an exhaust or ventilating system shall discharge to the outside atmosphere, provided that the exhaust system shall discharge to the outer air in such a manner that it will not cause a harmful exposure in any accessible workplace. Collecting systems which return air to work areas may be used if contaminants which accumulate in the work area air do not result in harmful exposure to employees.

(2) The air exhausted from blast-cleaning equipment, grinding, buffing, polishing equipment and all other equipment requiring exhausting of dust or particulate shall be discharged through dust-collecting equipment. Dust and refuse discharged from an exhaust system shall be disposed of in such a manner that it will not result in harmful exposure to employees.

NOTE: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.


1. New section filed 6-18-75; effective thirtieth day thereafter (Register 75, No. 25).

2. Amendment filed 12-13-84; effective thirtieth day thereafter (Register 84, No. 50).

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