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Subchapter 7. General Industry Safety Orders
Group 26. DIVING AND PRESSURIZED
ARTICLE 154. PRESSURIZED WORKSITE OPERATIONS
The following definitions shall apply in the application of these Orders.
Air Lock (Personnel): A chamber through which employees pass from one air pressure environment into another.
Bulkhead: An airtight structure separating the working chamber from free air or from another chamber under a different pressure than the working pressure.
Caisson: A wood, steel, concrete or reinforced air and water-tight chamber in which it is possible for employees to work under air pressure greater than
Compressed Air Environment (Hyperbaric Condition): A work site where the ambient pressure is greater than the atmospheric pressure at the entrance to the work site.
Decanting (surface decompression): A method used for decompressing under certain circumstances. In this procedure the workers are brought to atmospheric pressure with a very high gas tension in the tissues and then immediately re-compressed in a second and separate chamber or lock.
Division: The current Division of Occupational Safety and Health, any predecessors, or any subsequent successor agency.
Emergency Locks: A lock designed to hold and permit the quick passage of an entire shift of employees.
High Air: Air pressure used to supply power to pneumatic tools and devices.
Low Air: Air supplied to pressurize working chambers and locks.
Materials Lock: An air lock through which materials and equipment pass from one air pressure environment into another.
Hyperbaric Chamber: A chamber in which employees are treated for decompression sickness and/or air embolism. It may also be used in pre-employment physical examinations to determine the adaptability of the prospective employee to changes in pressure.
Pressure: A force acting on a unit area. Usually shown as pounds per square
Absolute Pressure (psi): The sum of the atmospheric pressure and gauge pressure (psig).
Ambient Pressure: Encompassing pressure surrounding all sides.
Atmospheric Pressure: The pressure of air at sea level, usually 14.7 psi (one atmosphere), or 0 Psig.
Gauge Pressure (psig): That pressure measured by a gauge and indicating the pressure exceeding atmospheric.
Safety Screen: An air- and water-tight diaphragm placed across the upper part of a compressed air tunnel between the face and bulkhead, in order to prevent flooding the crown of the tunnel between the safety screen and the bulkhead, thus providing a safe means of refuge and exit from a flooding or flooded tunnel.
Special Decompression Chamber: A chamber to provide greater comfort for employees when the total decompression time exceeds 75 minutes.
Supervising Physician: A physician licensed in the State of California who is familiar with and experienced in the physical requirements for the medical aspects of work in compressed air environments.
Working Chamber: The space or compartment under air pressure in which the work is being done.
Note: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.
1. New section filed 4-4-2006; operative 5-4-2006 (Register 2006, No. 14).
2. Repealer of definition of "Normal Condition" and new definition of
"Supervising Physician" filed 3-10-2010; operative 4-9-2010 (Register 2010,
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