Chapter 4, Subchapter 3, Article 3, Section 1205; Article 4, Section 1210;
Article 5, Section 1220; and Article 7, Section 1230


On April 6, 1979, Federal OSHA promulgated Subpart S-Underground Construction, Caissons, Cofferdams and Compressed Air (29 CFR 1926.803), which contains various regulations including the federal regulations addressing employees who work in compressed air environments. California’s comparable compressed air regulations, which include caisson requirements, are contained in Title 8, Compressed Air Safety Orders commencing with Sections 1200-1280 and Article 12, Appendix A tables containing suggestions for the Guidance of Compressed Air Workers.

Board staff performed a side-by-side code comparison of the two standards to identify Title 8 regulations which are either inconsistent with current industry practice (outdated requirements) or which are not at least as effective as (ALAEA) the federal standard. Results of Board staff’s evaluation of California’s standard indicates that the Compressed Air Safety Orders are not out of date or "in conflict" with current industry practices and that they are comparable in addressing issues addressed by the Federal Standard, with the exception of the following issues: on-site employee supervision by competent persons, maximum allowable employee air pressure exposure, role of on-site physician and air lock attendant, maintenance of air lock pressure gauge graphs, air lock ventilation, electrical installations, caisson sanitation, monitoring for airborne contaminants and the use of purified forced air ventilation during decompression.

The proposal contains an amendment, which is made entirely for the sake of clarity in Section 1230(b), which informs the employer that all electrical installations/equipment used in conjunction with compressed air work are to meet the applicable requirements of the Electrical Safety Orders. This proposed language is intended to address the issues described in the Federal regulation 29CFR1926.803(j), which pertains to electrical installations/equipment (e.g. lamps, wiring, grounding, etc.) instead of incorporating additional federal language.

Finally, Board staff notes that after comparing the State and Federal Appendices containing the decompression tables, staff finds the state and federal tables contain identical values. California goes one step beyond Federal OSHA and includes an Appendix B, which contains a decompression table (Table 3) designed for situations where employees are exposed to repetitive decompressions (more than once within a 12–hour period).


The proposed revisions to Sections 1205, 1210, 1220, and 1230 will make these regulations at least as effective as the federal counterpart regulations as contained in 29 CFR 1926.803(a)(1), (e)(5), (g)(l)(ii), (g)(l)(v), (g)(l)(xiii), (i)(2), (i)(4), (j)(1-6), and (k)(3).

The proposed revisions are as follows:

Section 1205. General Provisions

Existing Section 1205 requires the employer to notify the Division of Occupational Safety and Health in writing 7 days prior to undertaking compressed air work. This Section also requires the employer to have a qualified person familiar with the Compressed Air Safety Orders and other applicable orders on site at all times, while employees work in a compressed air environment.

A revision is proposed in subsection (b) to delete the word "qualified" and replace it with the term "competent."

The proposed revision is necessary to ensure that employees working in a compressed air environment will not be exposed to existing or anticipated hazards, by having their work overseen by a person with the authority and technical knowledge to correct any unsafe condition.

Section 1210. Compression Rate

This section consists of a single subsection (a), which prohibits the air pressure in an air lock from being increased to more than 3 pounds per square inch gauge (psig) within the first minute of employee compression. Subsection (a) also requires the pressure to be held at 3 psig and again at 7 psig, raising the pressure uniformly at a rate not to exceed 10 psig per minute. Furthermore, subsection (a) requires holding the pressure in the event an employee experiences discomfort, gradually reducing the pressure until employee’s signs of discomfort stops, releasing employees from the air lock in cases where the discomfort does not stop.

A new subsection (b) is proposed, which prohibits employees from being subjected to pressure exceeding 50 pounds per square inch except in an emergency.

The proposed subsection (b) is necessary to prevent excessive exposure to atmospheric compression, which could cause serious physical injury to the employee’s cardiovascular/musculoskeletal system, except in situations of last resort (emergencies).

Section 1220. Air Locks

This section requires employers to prohibit employees from passing from the working chamber of an air lock (lock) to atmospheric pressure until after decompression in accordance with the procedures specified in Appendix A, B or Section 1217 have been performed, except in emergency situations. Existing Section 1220 also addressed the following issues: posting of decompression time in air locks, duties/responsibilities/use of air lock attendants, use of automatic controls, use of manual controls, record keeping, use of pressure gauges, clocks, thermometers, minimum number of air locks required for specific tunnel operations, design of air locks, air lock illumination, etc.

Subsection (c) requires lock attendants to be stationed at the lock controls on the free air side during compression/decompression. The regulation specifies that the lock attendant is to remain in the vicinity of the air lock when employees are in the lock.

A revision is proposed to reword subsection (c) to require lock attendants to be under the supervision of a physician (already required per Section 1280) stationed at the lock controls, on the free airside during compression/decompression. The proposed revision would also require the lock attendant to be at the lock’s control station when employees are in the lock.

The proposed revision is necessary to prevent employees undergoing compression/decompression from experiencing accelerated physical stress, which could cause serious physical injury and/or permanent damage.

Subsection (g) requires a clock, thermometer and a continuous recording pressure gauge with 4-hour graph to be installed outside each air lock. This subsection also requires the graph to be visible to the lock attendant. In addition, a pressure gauge, clock and thermometer is to be installed in each air lock along with fittings to install additional test gauges as necessary.

A revision is proposed in subsection (g) to require a copy of the graph mentioned above to be submitted to the jobsite’s physician after each shift.

The proposed revision is necessary in order to allow the on-site physician to carefully monitor the function of the chamber, where the decompression/compression takes place and ensure the employee is not harmed by the pressure changes.

A new subsection (p) is proposed, which requires employers to provide adequate ventilation in accordance with Section 5143 of the General Industry Safety Orders.

The proposed subsection (p) is necessary to ensure employees are provided with an air supply free from contaminants, which if inhaled and introduced to the body systematically could cause serious illness and/or loss of consciousness.

Section 1230. Temperature, Illumination, Sanitation and Ventilation

Existing Section1230 addresses working chamber temperatures, illumination in chambers using electricity and independent electric-lighting systems with independent power supply, minimimun intensity of illumination for working surfaces, use of dressing rooms and drying rooms including lockers, bathing accommodations, toilets, water supply, etc. In addition, Section 1230 requires exhaust valves/pipes to be provided to ensure good working chamber ventilation, thus avoiding dead air pockets. It also requires ventilating air to be not less than 30 cubic feet per minute per person.

Revisions are proposed to add clarifying language in subsection (b) which informs the employer that all electrical installations/equipment are to comply with applicable portions of the Electrical Safety Orders.

The proposed revision is necessary to clarify to the employer that electrical installations, equipment, (e.g. lighting fixtures, wiring, etc.) are to be installed and used in accordance with the Electrical Safety Orders, to prevent employee injury and electrocution.

Subsection (d) contains requirements pertaining to the design of dressing rooms, drying rooms (compressed air environments) including benches, lockers, showers, hot/cold water, toilets and toilet design, when used in atmospheric pressures, which vary from normal atmospheric pressure.

A revision is proposed to add a sentence at the end of subsection (d), which would require all parts of caissons and other working compartments to be kept in a sanitary condition.

The proposed revision is necessary to prevent employees from being exposed to a variety of sanitation related illnesses, which could be contracted and spread in the working chambers/compartments as a result of the build up of waste material.

A new subsection (g) is proposed to require air in the caisson/working compartments (working chamber) categorized as "the workplace", to be periodically analyzed (once each shift) to ensure airborne contaminants are within the Permissible Exposure Limits (PEL’s) specified in Section 5155 of the General Industry Safety Orders. This revision also includes a requirement that records of the air analysis be kept on file at the location, where the work is being performed, and that test results must also be within 10% of the Lower Explosive Limit (LEL) for flammable gasses.

The proposed revision is necessary to ensure employees working in compressed air environments are not exposed to an atmospheric environment which could support an explosion, and that they are not exposed to levels of air borne contaminants at levels which could cause physical discomfort and/or illness.

A new subsection (k) is proposed which would require forced air ventilation during decompression via chemical or mechanical air purifying devices to ensure fresh air is provided.

The proposal is necessary to ensure that employees working in compressed air environments do not become ill as a result of impure air or air which is odorous and difficult to breathe.


  1. 29 CFR Ch. XVIII (7-1-97 Edition), 1926.803 Compressed Air, pages 443-461.

This document is available for review during normal business hours at the Standards Board Office located at 1300 I Street, Suite 920, Sacramento, California.

Documents Incorporated by Reference




It is anticipated that the proposed revisions will create no significant cost impact upon employers who engage in operations where employees are exposed to compressed air (e.g., caissons, air locks, etc.). When compared to the overall operation costs involved with employees who work at pressures that differ from atmospheric pressure, (typical costs measured in the tens or hundreds of thousands of dollars), compliance with the proposed air monitoring, ventilation, and the competent person requirement is expected to be insignificant. The remainder of the proposal consists of technical/clarifying changes or changes in administrative procedures that are also not expected to result in negative fiscal impact. This proposal is intended to correct regulatory deficiencies between state and federal compressed air regulations.

At most, some employers will need to assign personnel who are better trained to oversee employees working in compressed air environment and are able to recognize hazards and have the authority to take action when needed. Such personnel may also be responsible for performing periodic air monitoring to ensure airlocks, working chambers, compartments, etc. are not contaminated with airborne substances above current permissible limits (PEL’s). Technically, Section 5155 of the General Industry Safety Orders requires employers to ensure that the airborne contaminants are kept at levels that are considered safe. The proposed language clarifies that this requirement applies in compressed air work.


This proposal does not mandate the use of specific technology or equipment.


Costs or Savings to State Agencies

No costs or savings to state agencies will result as a consequence of the proposed revision to Sections 1205, 1210,1220, and 1230. This proposal consists of technical/clarifying revisions and because state agencies do not conduct below ground/water operations in which employees work in compressed air environments. Such work is generally contracted out to specialized contractors in the private sector.

Impact on Housing Costs

This proposal will not significantly affect housing costs.

Impact on Businesses

None (see explanation under "Identified Alternatives That Would Lessen Adverse Impact on Small Businesses").

Cost Impact on Private Persons or Entities

None (see explanation under "Identified Alternatives That Would Lessen Adverse Impact on Small Businesses").

Costs or Savings in Federal Funding to the State

The proposal will not result in costs or savings in federal funding to the state.

Costs or Savings to Local Agencies or School Districts Required to be Reimbursed

No costs to local agencies or school districts are required to be reimbursed. See explanation under "Determination of Mandate" and "Impact on Businesses."

Other Nondiscretionary Costs or Savings Imposed on Local Agencies

This proposal does not impose nondiscretionary costs or savings on local agencies. See explanation under "Costs or Savings to State Agencies" and "Impact on Businesses."


The Occupational Safety and Health Standards Board has determined that the proposed regulations do not impose a mandate requiring reimbursement by the state pursuant to Part 7 (commencing with Section 17500) of Division 4 of the Government Code because the proposed amendments will not require local agencies or school districts to incur additional costs in complying with the proposal. Furthermore, these regulations do not constitute a "new program or higher level of service of an existing program within the meaning of Section 6 of Article XIII B of the California Constitution."

The California Supreme Court has established that a "program" within the meaning of Section 6 of Article XIII B of the California Constitution is one which carries out the governmental function of providing services to the public, or which to implement a state policy, imposes unique requirements on local governments and does not apply generally to all residents and entities in the state. (County of Los Angeles v. State of California (1987) 43 Cal. 3d 46.)

These proposed regulations do not require local agencies to carry out the governmental function of providing services to the public. Rather, these regulations require local agencies to take certain steps to ensure the safety and health of their own employees only. Moreover, these proposed regulations do not in any way require local agencies to administer the California Occupational Safety and Health program. (See City of Anaheim v. State of California (1987) 189 Cal. App. 3d 1478.)

These proposed regulations do not impose unique requirements on local governments. All employers – state, local and private – will be required to comply with the prescribed standards.


It has been determined that the proposal may affect small business. The express terms of the proposal written in plain English have been prepared by the Board pursuant to Government Code Sections 11342 (e) and 11346.2 (a) (1) and the informative digest for this proposal constitutes a plain English overview.


The adoption of the proposed amendments to these regulations will neither create nor eliminate jobs in the State of California nor result in the elimination of existing businesses or create or expand businesses in the State of California.


No alternatives considered by the Board would be more effective in carrying out the purpose for which the action is proposed or would be as effective and less burdensome to affected private persons than the proposed action.