OSHA equipment Requirements for Rebreathers

shell-back

Has any one seen this before :
Appendix C to Subpart T of Part 1910 -- Alternative Conditions Under § 1910.401(a)(3) for Recreational Diving Instructors and Diving Guides (Mandatory)

Paragraph (a)(3) of § 1910.401 specifies that an employer of recreational diving instructors and diving guides (hereafter, "divers" or "employees") who complies with all of the conditions of this appendix need not provide a decompression chamber for these divers as required under §§ 1910.423(b)(2) or (c)(3) or 1910.426(b)(1).

1. Equipment Requirements for Rebreathers

(a) The employer must ensure that each employee operates the rebreather (i.e., semi-closed-circuit and closed-circuit self-contained underwater breathing apparatuses (hereafter, "SCUBAs")) according to the rebreather manufacturer's instructions.

(b) The employer must ensure that each rebreather has a counterlung that supplies a sufficient volume of breathing gas to their divers to sustain the divers' respiration rates, and contains a baffle system and/or other moisture separating system that keeps moisture from entering the scrubber.

(c) The employer must place a moisture trap in the breathing loop of the rebreather, and ensure that:

(i) The rebreather manufacturer approves both the moisture trap and its location in the breathing loop; and

(ii) Each employee uses the moisture trap according to the rebreather manufacturer's instructions.

(d) The employer must ensure that each rebreather has a continuously functioning moisture sensor, and that:

(i) The moisture sensor connects to a visual (e.g., digital, graphic, analog) or auditory (e.g., voice, pure tone) alarm that is readily detectable by the diver under the diving conditions in which the diver operates, and warns the diver of moisture in the breathing loop in sufficient time to terminate the dive and return safely to the surface; and

(ii) Each diver uses the moisture sensor according to the rebreather manufacturer's instructions.

(e) The employer must ensure that each rebreather contains a continuously functioning CO2 sensor in the breathing loop, and that:

(i) The rebreather manufacturer approves the location of the CO2 sensor in the breathing loop;

(ii) The CO2 sensor is integrated with an alarm that operates in a visual (e.g., digital, graphic, analog) or auditory (e.g., voice, pure tone) mode that is readily detectable by each diver under the diving conditions in which the diver operates; and

(iii) The CO2 alarm remains continuously activated when the inhaled CO2 level reaches and exceeds 0.005 atmospheres absolute (ATA).

(f) Before each day's diving operations, and more often when necessary, the employer must calibrate the CO2 sensor according to the sensor manufacturer's instructions, and ensure that:

(i) The equipment and procedures used to perform this calibration are accurate to within 10% of a CO2 concentration of 0.005 ATA or less;

(ii) The equipment and procedures maintain this accuracy as required by the sensor manufacturer's instructions; and

(iii) The calibration of the CO2 sensor is accurate to within 10% of a CO2 concentration of 0.005 ATA or less.

(g) The employer must replace the CO2 sensor when it fails to meet the accuracy requirements specified in paragraph 1(f)(iii) of this appendix, and ensure that the replacement CO2 sensor meets the accuracy requirements specified in paragraph 1(f)(iii) of this appendix before placing the rebreather in operation.

(h) As an alternative to using a continuously functioning CO2 sensor, the employer may use a schedule for replacing CO2-sorbent material provided by the rebreather manufacturer. The employer may use such a schedule only when the rebreather manufacturer has developed it according to the canister- testing protocol specified below in Condition 11, and must use the canister within the temperature range for which the manufacturer conducted its scrubber canister tests following that protocol. Variations above or below the range are acceptable only after the manufacturer adds that lower or higher temperature to the protocol.

(i) When using CO2-sorbent replacement schedules, the employer must ensure that each rebreather uses a manufactured (i.e., commercially pre-packed), disposable scrubber cartridge containing a CO2-sorbent material that:

(i) Is approved by the rebreather manufacturer;

(ii) Removes CO2 from the diver's exhaled gas; and

(iii) Maintains the CO2 level in the breathable gas (i.e., the gas that a diver inhales directly from the regulator) below a partial pressure of 0.01 ATA.

(j) As an alternative to manufactured, disposable scrubber cartridges, the employer may fill CO2 scrubber cartridges manually with CO2-sorbent material when:

(i) The rebreather manufacturer permits manual filling of scrubber cartridges;

(ii) The employer fills the scrubber cartridges according to the rebreather manufacturer's instructions;

(iii) The employer replaces the CO2-sorbent material using a replacement schedule developed under paragraph 1(h) of this appendix; and

(iv) The employer demonstrates that manual filling meets the requirements specified in paragraph 1(i) of this appendix.

(k) The employer must ensure that each rebreather has an information module that provides:

(i) A visual (e.g., digital, graphic, analog) or auditory (e.g., voice, pure tone) display that effectively warns the diver of solenoid failure (when the rebreather uses solenoids) and other electrical weaknesses or failures (e.g., low battery voltage);

(ii) For a semi-closed circuit rebreather, a visual display for the partial pressure of CO2, or deviations above and below a preset CO2 partial pressure of 0.005 ATA; and

(iii) For a closed-circuit rebreather, a visual display for: partial pressures of O2 and CO2, or deviations above and below a preset CO2 partial pressure of 0.005 ATA and a preset O2 partial pressure of 1.40 ATA or lower; gas temperature in the breathing loop; and water temperature.

(l) Before each day's diving operations, and more often when necessary, the employer must ensure that the electrical power supply and electrical and electronic circuits in each rebreather are operating as required by the rebreather manufacturer's instructions.

2. Special Requirements for Closed-Circuit Rebreathers

(a) The employer must ensure that each closed-circuit rebreather uses supply-pressure sensors for the O2 and diluent (i.e., air or nitrogen) gases and continuously functioning sensors for detecting temperature in the inhalation side of the gas-loop and the ambient water.

(b) The employer must ensure that:

(i) At least two O2 sensors are located in the inhalation side of the breathing loop; and

(ii) The O2 sensors are: functioning continuously; temperature compensated; and approved by the rebreather manufacturer.

(c) Before each day's diving operations, and more often when necessary, the employer must calibrate O2 sensors as required by the sensor manufacturer's instructions. In doing so, the employer must:

(i) Ensure that the equipment and procedures used to perform the calibration are accurate to within 1% of the O2 fraction by volume;

(ii) Maintain this accuracy as required by the manufacturer of the calibration equipment;

(iii) Ensure that the sensors are accurate to within 1% of the O2 fraction by volume;

(iv) Replace O2 sensors when they fail to meet the accuracy requirements specified in paragraph 2(c)(iii) of this appendix; and

(v) Ensure that the replacement O2 sensors meet the accuracy requirements specified in paragraph 2(c)(iii) of this appendix before placing a rebreather in operation.

(d) The employer must ensure that each closed-circuit rebreather has:

(i) A gas-controller package with electrically operated solenoid O2-supply valves;

(ii) A pressure-activated regulator with a second-stage diluent-gas addition valve;

(iii) A manually operated gas-supply bypass valve to add O2 or diluent gas to the breathing loop; and

(iv) Separate O2 and diluent-gas cylinders to supply the breathing-gas mixture.

3. O2 Concentration in the Breathing Gas

The employer must ensure that the fraction of O2 in the nitrox breathing-gas mixture:

(a) Is greater than the fraction of O2 in compressed air (i.e., exceeds 22% by volume);

(b) For open-circuit SCUBA, never exceeds a maximum fraction of breathable O2 of 40% by volume or a maximum O2 partial pressure of 1.40 ATA, whichever exposes divers to less O2; and

(c) For a rebreather, never exceeds a maximum O2 partial pressure of 1.40 ATA.

4. Regulating O2 Exposures and Diving Depth

(a) Regarding O2 exposure, the employer must:

(i) Ensure that the exposure of each diver to partial pressures of O2 between 0.60 and 1.40 ATA does not exceed the 24-hour single-exposure time limits specified either by the 2001 National Oceanic and Atmospheric Administration Diving Manual (the "2001 NOAA Diving Manual"), or by the report entitled "Enriched Air Operations and Resource Guide" published in 1995 by the Professional Association of Diving Instructors (known commonly as the "1995 DSAT Oxygen Exposure Table"); and

(ii) Determine a diver's O2-exposure duration using the diver's maximum O2 exposure (partial pressure of O2) during the dive and the total dive time (i.e., from the time the diver leaves the surface until the diver returns to the surface).

(b) Regardless of the diving equipment used, the employer must ensure that no diver exceeds a depth of 130 feet of sea water ("fsw") or a maximum O2 partial pressure of 1.40 ATA, whichever exposes the diver to less O2.

5. Use of No-Decompression Limits

(a) For diving conducted while using nitrox breathing-gas mixtures, the employer must ensure that each diver remains within the no-decompression limits specified for single and repetitive air diving and published in the 2001 NOAA Diving Manual or the report entitled "Development and Validation of No-Stop Decompression Procedures for Recreational Diving: The DSAT Recreational Dive Planner," published in 1994 by Hamilton Research Ltd. (known commonly as the "1994 DSAT No-Decompression Tables").

(b) An employer may permit a diver to use a dive-decompression computer designed to regulate decompression when the dive- decompression computer uses the no-decompression limits specified in paragraph 5(a) of this appendix, and provides output that reliably represents those limits.

6. Mixing and Analyzing the Breathing Gas

(a) The employer must ensure that:

(i) Properly trained personnel mix nitrox-breathing gases, and that nitrogen is the only inert gas used in the breathing-gas mixture; and

(ii) When mixing nitrox-breathing gases, they mix the appropriate breathing gas before delivering the mixture to the breathing-gas cylinders, using the continuous-flow or partial-pressure mixing techniques specified in the 2001 NOAA Diving Manual, or using a filter-membrane system.

(b) Before the start of each day's diving operations, the employer must determine the O2 fraction of the breathing-gas mixture using an O2 analyzer. In doing so, the employer must:

(i) Ensure that the O2 analyzer is accurate to within 1% of the O2 fraction by volume.

(ii) Maintain this accuracy as required by the manufacturer of the analyzer.

(c) When the breathing gas is a commercially supplied nitrox breathing-gas mixture, the employer must ensure that the O2 meets the medical USP specifications (Type I, Quality Verification Level A) or aviator's breathing-oxygen specifications (Type I, Quality Verification Level E) of CGA G-4.3-2000 ("Commodity Specification for Oxygen"). In addition, the commercial supplier must:

(i) Determine the O2 fraction in the breathing-gas mixture using an analytic method that is accurate to within 1% of the O2 fraction by volume;

(ii) Make this determination when the mixture is in the charged tank and after disconnecting the charged tank from the charging apparatus;

(iii) Include documentation of the O2-analysis procedures and the O2 fraction when delivering the charged tanks to the employer.

(d) Before producing nitrox breathing-gas mixtures using a compressor in which the gas pressure in any system component exceeds 125 pounds per square inch (psi), the:

(i) Compressor manufacturer must provide the employer with documentation that the compressor is suitable for mixing high- pressure air with the highest O2 fraction used in the nitrox breathing-gas mixture when operated according to the manufacturer's operating and maintenance specifications;

(ii) Employer must comply with paragraph 6(e) of this appendix, unless the compressor is rated for O2 service and is oil- less or oil-free; and

(iii) Employer must ensure that the compressor meets the requirements specified in paragraphs (i)(1) and (i)(2) of § 1910.430 whenever the highest O2 fraction used in the mixing process exceeds 40%.

(e) Before producing nitrox breathing-gas mixtures using an oil- lubricated compressor to mix high-pressure air with O2, and regardless of the gas pressure in any system component, the:

(i) Employer must use only uncontaminated air (i.e., air containing no hydrocarbon particulates) for the nitrox breathing-gas mixture;

(ii) Compressor manufacturer must provide the employer with documentation that the compressor is suitable for mixing the high- pressure air with the highest O2 fraction used in the nitrox breathing-gas mixture when operated according to the manufacturer's operating and maintenance specifications;

(iii) Employer must filter the high-pressure air to produce O2-compatible air;

(iv) The filter-system manufacturer must provide the employer with documentation that the filter system used for this purpose is suitable for producing O2-compatible air when operated according to the manufacturer's operating and maintenance specifications; and

(v) Employer must continuously monitor the air downstream from the filter for hydrocarbon contamination.

(f) The employer must ensure that diving equipment using nitrox breathing-gas mixtures or pure O2 under high pressure (i.e., exceeding 125 psi) conforms to the O2-service requirements specified in paragraphs (i)(1) and (i)(2) of § 1910.430.

7. Emergency Egress

(a) Regardless of the type of diving equipment used by a diver (i.e., open-circuit SCUBA or rebreathers), the employer must ensure that the equipment contains (or incorporates) an open-circuit emergency-egress system (a "bail-out" system) in which the second stage of the regulator connects to a separate supply of emergency breathing gas, and the emergency breathing gas consists of air or the same nitrox breathing-gas mixture used during the dive.

(b) As an alternative to the "bail-out" system specified in paragraph 7(a) of this appendix, the employer may use:

(i) For open-circuit SCUBA, an emergency-egress system as specified in § 1910.424(c)(4); or

(ii) For a semi-closed-circuit and closed-circuit rebreather, a system configured so that the second stage of the regulator connects to a reserve supply of emergency breathing gas.

(c) The employer must obtain from the rebreather manufacturer sufficient information to ensure that the bail-out system performs reliably and has sufficient capacity to enable the diver to terminate the dive and return safely to the surface.

8. Treating Diving-Related Medical Emergencies



11. Testing Protocol for Determining the CO2 Limits of Rebreather Canisters

(a) The employer must ensure that the rebreather manufacturer has used the following procedures for determining that the CO2-sorbent material meets the specifications of the sorbent material's manufacturer:

(i) The North Atlantic Treating Organization CO2 absorbent-activity test;

(ii) The RoTap shaker and nested-sieves test;

(iii) The Navy Experimental Diving Unit ("NEDU")-derived Schlegel test; and

(iv) The NEDU MeshFit software.

(b) The employer must ensure that the rebreather manufacturer has applied the following canister-testing materials, methods, procedures, and statistical analyses:

(i) Use of a nitrox breathing-gas mixture that has an O2 fraction maintained at 0.28 (equivalent to 1.4 ATA of O2 at 130 fsw, the maximum O2 concentration permitted at this depth);

(ii) While operating the rebreather at a maximum depth of 130 fsw, use of a breathing machine to continuously ventilate the rebreather with breathing gas that is at 100% humidity and warmed to a temperature of 98.6 degrees F (37 degrees C) in the heating- humidification chamber;

(iii) Measurement of the O2 concentration of the inhalation breathing gas delivered to the mouthpiece;

(iv) Testing of the canisters using the three ventilation rates listed in Table I below (with the required breathing-machine tidal volumes and frequencies, and CO2-injection rates, provided for each ventilation rate):




Ventilation rates (Lpm, ATPS(1))

22.5
40.0
62.5
Breathing machine tidal volumes (L)
1.5
2.0
2.5
Breathing machine frequencies (breaths per min.)
15
20
25
CO2 injection rates (Lpm, STPD \2\)
0.90
1.35
2.25





1 ATPS means ambient temperature and pressure, saturated with water.
2 STPD means standard temperature and pressure, dry; the standard temperature is 32 degrees F (0 degrees C).

(v) When using a work rate (i.e., breathing-machine tidal volume and frequency) other than the work rates listed in the table above, addition of the appropriate combinations of ventilation rates and CO2-injection rates;

(vi) Performance of the CO2 injection at a constant (steady) and continuous rate during each testing trial;

(vii) Determination of canister duration using a minimum of four (4) water temperatures, including 40, 50, 70, and 90 degrees F (4.4, 10.0, 21.1, and 32.2 degrees C, respectively);

(viii) Monitoring of the breathing-gas temperature at the rebreather mouthpiece (at the "chrome T" connector), and ensuring that this temperature conforms to the temperature of a diver's exhaled breath at the water temperature and ventilation rate used during the testing trial; (1)



(ix) Implementation of at least eight (8) testing trials for each combination of temperature and ventilation-CO2- injection rates (for example, eight testing trials at 40 degrees F using a ventilation rate of 22.5 Lpm at a CO2-injection rate of 0.90 Lpm);

(x) Allowing the water temperature to vary no more than 2.0 degrees F ( 1.0 degree C) between each of the eight testing trials, and no more than 1.0 degree F ( 0.5 degree C) within each testing trial;

(xi) Use of the average temperature for each set of eight testing trials in the statistical analysis of the testing-trial results, with the testing-trial results being the time taken for the inhaled breathing gas to reach 0.005 ATA of CO2 (i.e., the canister-duration results);

(xii) Analysis of the canister-duration results using the repeated-measures statistics described in NEDU Report 2-99;

(xiii) Specification of the replacement schedule for the CO2-sorbent materials in terms of the lower prediction line (or limit) of the 95% confidence interval; and

(xiv) Derivation of replacement schedules only by interpolating among, but not by extrapolating beyond, the depth, water temperatures, and exercise levels used during canister testing.

[FR Doc. 04-3289 Filed 2-13-04; 8:45 am]

BILLING CODE 4510-26-P


Footnote 1 ATA is the partial pressure of a constituent gas in the total pressure of a breathing gas. When the percentage of the constituent gas in the breathing gas remains constant throughout a dive, its partial pressure, or ATA, increases in direct proportion to increases in diving depth. (Back to text)

dantheman

silentscuba

Wow!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!

__________________
Curt McNamee
rEvo CCR Diver
KISS CCR Diver
www.silentscuba.com

caveseeker7

No.

Couldn't have expressed it better.

That's really the bottom line, isn't it.

__________________
Cheers
Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority,
and rabidly promoted by an unscrupulous mainstream media,
which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"

denzel

This is a joke ok?
If not, move. leave the country, your leaders are soft in the head.

denz.

__________________

edster

So for anyone who has a moisture and CO2 sensor equipped Rebreather, you are now free to dive. Everyone else, go home.

This cant be law, surely? My gob is truly smacked if it is...

__________________

jradomski

They have been around a while I made a post on scubaboard 4-09-2003 about this "standard" The good thing about the rules is that there are no absolutes to limit the uses since most of the guidlines dont have a reasonable solution, and I'm not even sure its been officially adopted, last time I pulled the document it was a "proposal for a rule change", but definately not official policy..


I'm not posting the link because I rather not bring this old thread back to life, I know stephan didn;t like the old thread..


like the co2 sensor need... you need it but if you dont you have to go by strickt endurance of scrubber ratings..

__________________
Joe Radomski
CCR Trimix Instructor Trainer
ANDI Instructor Trainer Director #10

All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.

AD_ward9

It is not law, it is a proposal. (Since posting: I stand corrected. This has been around for years as a proposal, but from posts below, it seems it is now a regulation, but apparently not enforced. )

The HSE have a similar document.

In Europe, EN14143 requires that any CO2 sensor fitted is accurate to within 3% over all depth and gas mix ranges. Someone´s attempt to prevent CO2 monitors being sold.

Cheers,

Alex

shell-back

DEPARTMENT OF LABOR

Occupational Safety and Health Administration

29 CFR Part 1910

[Docket No. S-550]

RIN 1218-AB97

Commercial Diving Operations

AGENCY: Occupational Safety and Health Administration (OSHA), Department of Labor.

ACTION: Final rule. SUMMARY: OSHA is issuing this final rule to amend its Commercial Diving Operations (CDO) standards. This final rule allows employers of recreational diving instructors and diving guides to comply with an alternative set of requirements instead of the decompression-chamber requirements in the current CDO standards. The final rule applies only when these employees engage in recreational diving instruction and diving-guide duties; use an open-circuit, a semi-closed-circuit, or a closed-circuit self-contained underwater-breathing apparatus supplied with a breathing gas that has a high percentage of oxygen mixed with nitrogen; dive to a maximum depth of 130 feet of sea water; and remain within the no-decompression limits specified for the partial pressure of nitrogen in the breathing-gas mixture. These alternate requirements essentially are the same as the terms of a variance granted by OSHA to Dixie Divers, Inc. in 1999.

DATES: This final rule becomes effective on March 18, 2004.

ADDRESSES: In compliance with 28 U.S.C. 2112(a), OSHA designates the Associate Solicitor of Labor for Occupational Safety and Health as the recipient of petitions for review of this final rule. Submit petitions of review to the Associate Solicitor at: Office of the Solicitor of Labor, Room S-4004, U.S. Department of Labor, 200 Constitution Avenue, NW., Washington, DC 20210.

FOR FURTHER INFORMATION CONTACT: For general information and press inquiries, contact Mr. George Shaw, Office of Communications, Room N-3647, OSHA, U.S. Department of Labor, 200 Constitution Avenue, NW., Washington, DC 20210; telephone (202) 693-1999. For technical inquiries, contact Mr. Robert Bell, Directorate of Standards and Guidance, Room N-3609, OSHA, U.S. Department of Labor, 200 Constitution Avenue, NW., Washington, DC 20210; telephone (202) 693-2053 or fax (202) 693-1663.

Copies of this Federal Register notice are available from the OSHA Office of Publications, Room N-3101, U.S. Department of Labor, 200 Constitution Avenue, NW., Washington DC 20210; telephone (202) 693-1888. For an electronic copy of this notice, go to OSHA's Web site (http://www.osha.gov), and select "Federal Register," "Date of Publication," and then "2003."

SUPPLEMENTARY INFORMATION:

Table of Contents

The following Table of Contents identifies the major sections under Supplementary Information, including a detailed summary and explanation of the final rule.

I. Background
II. Summary and Explanation of the Rule

A. Final §§ 1910.401(a)(3) and 1910.402 ("Definitions")

B. Conditions Specified in Final Appendix C
III. Legal Considerations
IV. Final Economic Analysis and Regulatory Flexibility Certification
V. Paperwork Reduction Act
VI. Federalism
VII. State Plans
VIII. Unfunded Mandates
IX. Applicability of Existing Consensus Standards

List of Subjects in 29 CFR Part 1910
X. Authority and Signature


I. Background

In 1999, acting under section 6(d) of the Occupational Safety and Health Act of 1970 ("OSH Act" 29 U.S.C. 655), the Occupational Safety and Health Administration ("OSHA" or "the Agency") published an order granting a permanent variance to Dixie Divers, Inc. ("Dixie Divers") (Ex. 2-11). The permanent variance exempted Dixie Divers from OSHA's decompression-chamber requirements specified at § 1910.423(b)(2) and (c)(3)(iii), and § 1910.426(b)(1), when its recreational diving instructors and diving guides (hereafter, "divers") engage in underwater instructional and guiding operations.

The purpose of having a decompression chamber available and ready for use at a dive site is to treat decompression sickness (DCS) and arterial gas embolism (AGE). DCS may occur from breathing air or mixed gases at diving depths and durations that require decompression, while AGE may result from over-pressurizing the lungs, usually following a rapid ascent to the surface during a dive without proper exhalation.

The Dixie Diver variance from the decompression-chamber requirements applied only to mixed-gas diving operations at a maximum depth of 130 feet of sea water ("fsw") performed within no-decompression limits. During these diving operations, divers use a breathing-gas mixture consisting of a high percentage of O2 mixed with nitrogen (i.e., a nitrox breathing-gas mixture) supplied by an open-circuit, semi-closed-circuit or closed-circuit self-contained underwater breathing apparatus (SCUBA). In issuing the permanent variance, the Agency noted that compliance would provide divers with a level of protection that met or exceeded the level of protection they would receive if they had access to a decompression chamber at the dive site as required by §§ 1910.423(b)(2) and (c)(3)(iii), and 1910.426(b)(1).

On January 10, 2003, OSHA proposed to amend its Commercial Diving Operations ("CDO") standards to incorporate the terms and conditions of the Dixie Divers variance as an appendix to the CDO standards (68 FR 1399). The Agency now is issuing the final rule to amend the CDO standards based on this proposal. OSHA believes that this amendment enables recreational diving instructors and diving guides to extend their diving operations while minimizing their risk of DCS and AGE. The Agency concludes that the recreational diving instructors and diving guides covered by this amendment will receive a level of safety and health protection that is equivalent to recreational diving instructors and diving guides who have a decompression chamber located at the dive site during mixed-gas diving operations regulated under the CDO standards. Therefore, a decompression chamber near the dive site is unnecessary for the divers covered by this final rule.

II. Summary and Explanation of the Final Rule

OSHA received no requests for a hearing on the proposed amendment, thereby enabling it to proceed directly to this final rule after considering the comments submitted by the public in response to the proposal. In this regard, the Agency received 13 public comments on the proposal. However, two commenters each submitted a duplicate set of responses (Exs. 6-6 and 6-7, and 6-8 and 6-9); one set of duplicate responses (Exs. 6-6 and 6-7) was received from a commercial diver that involved an issue unrelated to this rulemaking. We address the remaining comments in sections A and B below, which discuss the conditions adopted in the final rule.

When the discussion regarding a condition does not cite a comment, then the public did not comment on that condition. In such cases, we have assumed that the regulated community found the proposed condition to be appropriate and necessary for diver safety based on OSHA's stated rationale in the proposed rule, and we have retained it in the final rule without further explanation (see 68 FR 1399, pages 1400-1409).

A. Final §§ 1910.401(a)(3) and 1910.402 ("Definitions")

Proposed § 1910.401(a)(3) specified that this amendment would apply only to recreational diving instructors and diving guides who are engaged solely in recreational diving instruction and dive-guiding operations. Accordingly, OSHA also proposed to add the following definitions for "recreational diving instruction" and "dive-guiding operations" to § 1910.402 of the CDO standards:

"Recreational diving instruction" means the training of diving students in the use of recreational diving procedures and the safe operation of diving equipment, including open-circuit, semi-closed-circuit, or closed-circuit SCUBA during dives.

"Dive-guiding operations" means the leading of groups of trained sports divers, who use open-circuit, semi-closed-circuit, or closed-circuit SCUBA, to local undersea diving locations for recreational purposes.

To further limit application of the amendment, proposed § 1910.401(a)(3) required employers to ensure that the instructors and guides conduct these dives within the no-decompression limits, and that they use a nitrox breathing-gas mixture consisting of a high percentage of O2 (more than 22% by volume) mixed with nitrogen and supplied by an open-circuit, semi-closed-circuit, or closed-circuit SCUBA. Under this proposed requirement, employers also would have to comply with the requirements specified in new Appendix C of subpart T.

Based on its analysis of the record, OSHA is adopting proposed §§ 1910.401(a)(3) and 1910.402 in the final rule. Recreational diving instructors and diving guides who use a nitrox breathing-gas mixture supplied by an open-circuit, semi-closed-circuit, or closed-circuit SCUBA under no-decompression diving limits will receive a level of safety and health protection equivalent to the recreational diving instructors and diving guides who have a decompression chamber located at the dive site during mixed-gas diving operations regulated under the CDO standards.

B. Conditions Specified in Final Appendix C

OSHA proposed to add a new appendix to the CDO standards to specify the conditions under which employers may use this alternative to decompression chambers. Accordingly, the Agency is adopting new Appendix C in the final rule after revising the proposal based on comments submitted to the record. The following discussion addresses the comments received on the proposed conditions, and what OSHA is including in the final rule.

1. Equipment Requirements for Rebreathers

(a) Manufacturer's instructions. As proposed, this condition required employers to ensure that their recreational diving instructors and diving guides use rebreathers (i.e., semi-closed circuit and closed-circuit SCUBA) according to the rebreather manufacturer's instructions. OSHA is retaining this condition in the final rule. As noted in the proposal, the Agency believes that SCUBA manufacturers are best qualified to identify and specify the components, configuration, and operation of their products.

(b) Counterlungs. This proposed condition required employers to ensure that each rebreather has a counterlung (also referred to as an "inhalation bag" or "breathing bag") that both contains a baffle system that prevents moisture from entering the scrubber or breathing hoses and supplies a sufficient volume of breathing gas to the divers to sustain their respiration rate during diving operations. The National Oceanic and Atmospheric Administration (NOAA) considers counterlungs a necessity for rebreather diving (see Ex. 3-12, p. 14-3). OSHA expects rebreather manufacturers to provide the purchaser or user with information regarding this displacement as part of their usual and customary practice. In addition, by keeping moisture from entering the scrubber, baffle systems prevent rapid deterioration of the CO2-sorbent material housed in the scrubber and decrease the risk of CO2 toxicity (see Ex. 3-12, p. 14-8).

The Agency received one comment (Ex. 5-2-1) regarding the proposed baffle-system requirement. This commenter recommended revising the condition to read that the counterlung must contain "a baffle system and/or other moisture separating system that keeps moisture from entering the scrubber." In justifying this revision, the commenter stated: "While all manufactured units have some sort of system to accomplish this function, all do not call it a "baffle" system. Additionally, use of the specific term may * * * create problems for future technological developments, which may address the problem in different ways." OSHA agrees with this commenter that the proposed wording was too specific, and might hinder future efforts to develop new technologies to prevent moisture from entering the scrubber. Therefore, the final rule adopts the language of the proposed condition except for the part addressing baffle systems; for this part, the Agency is adopting the language recommended by this commenter.

(c) Moisture traps. Under this proposed condition, employers need to place a moisture trap in the breathing loop of each rebreather. The employer also must ensure that the rebreather manufacturer approves both the moisture trap and its location in the breathing loop, and that their divers use the moisture trap according to the rebreather manufacturer's instructions. The Agency is retaining this condition in the final rule as proposed because it believes that moisture traps, when approved by the rebreather manufacturer and located and used according to the manufacturer's instructions, prevent water from entering the CO2-absorbing canisters. By preventing such water leakage, moisture traps preserve the CO2-absorbing properties of the sorbent material inside the canister.

(d) Moisture sensors. Under this proposed condition, employers must ensure that each rebreather has a continuously functioning moisture sensor that connects to a visual (e.g., digital, graphic, or analog) or auditory (e.g., voice, pure tone) alarm. This alarm must be readily detectable by divers under the diving conditions in which they operate and warn them of moisture in the breathing loop in sufficient time for them to terminate the dive and return safely to the surface. Additionally, the proposed condition required employers to ensure that their divers use the moisture sensors according to the rebreather manufacturer's instructions. By warning divers of hazardous water leakage into the canister, moisture sensors allow divers to return to the surface before CO2 in the recycled breathing gas reaches dangerous levels. Therefore, the final rule includes these requirements as proposed.

(e) CO2 sensors. An important component in controlling excessive CO2 is the CO2 sensor. In the proposal, this condition required employers to ensure that each rebreather contains a continuously functioning CO2 sensor in the breathing loop. It also specified that the rebreather manufacturer must approve the CO2 sensor and its location in the breathing loop. In addition, employers must ensure that the CO2 sensor is integrated with an alarm that operates in a visual (e.g., digital, graphic, or analog) or auditory (e.g., voice, pure tone) mode readily detectable by divers under the diving conditions in which they operate. This alarm would remain continuously activated when the inhaled CO2 level reaches and exceeds 0.005 atmospheres absolute ("ATA").(1) In the final rule, OSHA is retaining the condition as proposed.

(f) Calibrating CO2 sensors. This proposed condition stated that employers must, before each day's diving operations (and more often when necessary), calibrate each CO2 sensor according to the sensor manufacturer's instructions. Additionally, employers must maintain the accuracy of the equipment and procedures used to perform the calibration to within 10% of a CO2 concentration of 0.005 ATA or less according to the sensor manufacturer's instructions. Using this equipment, they would calibrate the CO2 sensor to within 10% of a CO2 concentration of 0.005 ATA or less. The Agency is including this condition in the final rule because it concludes that this calibration requirement is necessary to identify improperly functioning CO2 sensors.

(g) Faulty CO2 sensors. In the proposal, this condition specified that employers must replace CO2 sensors that fail the accuracy requirements delineated above in Condition 1(f)(iii) with a sensor that meets these requirements. Eliminating sensors that are unreliable or that cannot function under rugged diving conditions is necessary to provide divers with safe breathing gas. OSHA is retaining this requirement in the final rule.

(h) CO2-sorbent materials. As an alternative to using continuously functioning CO2 sensors, the proposed condition allowed an employer to implement a rebreather manufacturer's schedule for replacing the CO2-sorbent material in the canister of a rebreather. However, the manufacturer would have to develop the schedule according to the canister-testing protocol specified in Condition 11 of Appendix C ("Testing Protocol for Determining the CO2 Limits of Rebreather Canisters"). Additionally, the employer may use the rebreather at a water temperature that is lower than the minimum, or higher than the maximum, water temperature used in the testing protocol specified in Condition 11, but only when the rebreather manufacturer adds that lower or higher temperature to the testing protocol.

A commenter (Ex. 5-2-1) stated that the proposed language regarding the minimum and maximum water-temperature requirement was confusing, and recommended that the requirement read as follows: "A rebreather within the temperature range for which the manufacturer conducted its scrubber canister tests following the protocol specified in Condition 11. Variations above or below the range are acceptable only after the manufacturer adds that lower or higher temperature to the protocol." OSHA agrees that the commenter's revision expresses more clearly than the proposal the meaning of this provision, and has revised this language in the final rule accordingly. The Agency believes that the canister-replacement schedule provides a reliable estimate of canister duration that incorporates an assessment of the physical properties of the CO2-sorbent material and an evaluation of the canister's effectiveness.

(i) Commercially pre-packed cartridges. This proposed condition required employers who use a CO2-sorbent replacement schedule specified in Condition 1(h) to ensure that each rebreather uses a manufactured (i.e., commercially pre-packed), disposable scrubber cartridge. This cartridge would have to contain a CO2-sorbent material that is approved by the rebreather manufacturer and is capable of removing CO2 from the divers' exhaled gas. In this regard, the canister would maintain the CO2 level in the breathable gas (i.e., the gas a diver is inhaling directly from the regulator) below a partial pressure of 0.01 ATA.

OSHA is including this condition in the final rule as proposed. These requirements ensure proper compression and uniform distribution of the sorbent material in the cartridge, thereby minimizing "channeling" in the material (2) and lowering the diver's risk of rebreathing exhaled breathing gas that is high in CO2.

(j) Alternative to commercially pre-packed cartridges. This proposed condition permitted employers to fill CO2 scrubber cartridges manually instead of using commercially pre-packed cartridges. This practice is acceptable when the rebreather manufacturer designs the scrubber cartridge to be filled manually, the employer implements the alternative method according to the rebreather manufacturer's instructions, and the employer can demonstrate that the alternative method meets the performance requirements for commercially pre-packed cartridges specified by Conditions 1(h) and 1(i). OSHA is adopting this condition in the final rule as proposed because manually filled cartridges that meet the performance requirements for commercially pre-packed cartridges will remove CO2 effectively from the breathing loop.

(k) Information module. In the proposal, this condition required employers to ensure that their divers use an information module that provides them with critical information regarding rebreather operation. For all rebreathers, the module needed to contain visual or auditory warning devices that would alert the diver to electrical weaknesses or failures (e.g., solenoid failure, low battery levels). In addition, modules used in semi-closed circuit rebreathers needed to contain visual displays for the partial pressure of CO2, or deviations above and below a preset CO2 partial pressure of 0.005 ATA. For closed-circuit rebreathers, the module also would have visual displays for the partial pressures of O2 and CO2, or deviations above and below a preset CO2 partial pressure of 0.005 ATA and a preset O2 partial pressure of 1.40 ATA. The module also needed to have a visual display for both gas temperature in the breathing loop and water temperature.

OSHA is including these requirements in the final rule as proposed because warning divers of electrical weaknesses and failures informs them not to rely on their electrically operated equipment and to take protective actions. Providing information about O2 and CO2 partial pressures alerts divers to rising and potentially toxic levels of these gases in time for them to prevent extended exposure. Additionally, information regarding water temperature warns divers of the risk of hypothermia, while gas-temperature information allows divers to estimate the duration of their CO2-sorbent material.

(l) Checking electrical power and circuits. Under this proposed condition, employers would ensure that the electrical power supplies and electrical and electronic circuits in each rebreather are operating according to the rebreather manufacturer's instructions. Employers must check for proper operation prior to beginning diving operations each day, and more often when necessary. The Agency is adopting this condition as proposed because partial or total electronic failures could interfere with rebreather sensor and control systems.

2. Special Requirements for Closed-Circuit Rebreathers

(a) Supply-pressure and temperature sensors. This proposed condition stated that employers are responsible for ensuring that closed-circuit rebreathers use supply-pressure sensors for the O2 and diluent gases (i.e., air or nitrogen), as well as continuously functioning sensors for detecting temperature in the inhalation side of the breathing loop and in the ambient water. OSHA is including it in the final rule as proposed. In this regard, supply-pressure sensors inform divers of the remaining supply of breathing-gas ingredients (i.e., O2 and air or nitrogen), thereby enabling them to monitor their breathing-gas consumption during a dive. Low gas supplies alert divers to an unusually high consumption of breathing gas, indicating a possible problem with the rebreather. An unexpected gas loss also may increase the need for a diver to make a rapid (i.e., emergency) ascent to the surface during a dive, which could result in over-pressurization of the lungs associated with AGE. In addition, OSHA believes that temperature sensors increase diver safety because the sensors alert divers to the possibility of hypothermia. Temperature reductions in breathing gas also inform divers that the efficiency of the CO2-sorbent material is likely to deteriorate (Ex. 3-11).

(b) O2 sensors. As proposed, this condition required employers to ensure that at least two O2 sensors are located in the inhalation side of the breathing loop. These O2 sensors must function continuously, compensate for variations in temperature, and be approved by the rebreather manufacturer. The Agency is including the condition in the final rule as proposed because the sensors provide divers with critical information regarding O2 levels in the breathing gas. Accurate information about O2 levels enables divers to maintain appropriate amounts of O2 in the breathing gas, thereby minimizing the need for emergency escape.

(c) Calibrating O2 sensors. This proposed condition specified that employers must calibrate O2 sensors as required by the sensor manufacturer's instructions before the start of each day's diving operations and more often when necessary. In performing this requirement, employers would: (i) Ensure that the equipment and procedures used to perform the calibration are accurate to within 1% of the O2 fraction by volume; (ii) maintain the accuracy of the calibration equipment as required by the manufacturer of the equipment; (iii) ensure that the sensors are accurate to within 1% of the O2 fraction by volume; (iv) replace O2 sensors when they fail to meet the specified accuracy requirements; and (v) ensure that the replacement O2 sensors meet these accuracy requirements.

OSHA believes that the levels of accuracy specified under this condition provide an adequate safety margin for the divers to detect anomalous O2 concentrations, to identify the cause of the anomaly and adjust breathing-system controls accordingly, and to ascend to the surface when necessary. Additionally, proper and timely calibration of O2 sensors, as well as accurate information regarding the level of O2 in the breathing loop, provides divers with an opportunity to take corrective action should the O2 level exceed the specified parameters. Maintaining proper O2 levels will prevent the central nervous system and pulmonary effects of O2 toxicity, and will protect divers from death and injury. Accordingly, the Agency is including these O2-sensor requirements in the final rule as proposed.

(d) Controlling O2 delivery. This proposed condition stated that employers are to ensure that closed-circuit rebreathers have: (i) A gas-controller package with solenoid O2-supply valves that are operated electronically; (ii) a pressure-activated regulator with a second-stage diluent-gas addition valve; (iii) a manually-operated gas-supply bypass valve to add O2 and diluent gas to the breathing loop; and (iv) separate O2 and diluent-gas cylinders to supply the breathing-gas mixture. Accordingly, closed-circuit rebreathers would automatically inject O2 into the breathing loop to maintain the pre-established O2 partial pressure in the breathable gas, and automatically add diluent gas (i.e., nitrogen or air) through the regulator to compensate for decreases in gas volume during descent. The diver also must be able to control these functions manually using gas-supply bypass valves provided on the equipment. Separate cylinders would provide the O2 and diluent gas used in the breathing-gas mixture.

OSHA is adopting the condition as proposed because these equipment requirements maintain O2 levels in the breathing gas within a specified range of partial pressures. This condition provides assurance that a sufficient and reliable breathing-gas pressure is available to deliver breathable gas to the diver without adversely affecting breathing effort. Maintaining a comfortable breathing effort reduces CO2 accumulation caused by an increased rate of breathing and, in turn, lowers the risk of CO2 toxicity. Additionally, by maintaining O2 in the breathing loop at specified levels, the condition ensures that divers remain within pre- established O2 exposure limits. Finally, the condition allows divers to manually add O2 or diluent gas from separate cylinders, enabling them to adjust the components of the breathing-gas mixture should the gas-controller package and pressure- activated regulator fail.

3. O2 Concentration in the Breathing Gas

Under this proposed condition, employers would be responsible for ensuring that the fraction of O2 in the nitrox breathing-gas mixture exceeds 22% by volume.(3) For rebreathers, the fraction of O2 would never exceed an O2 partial pressure of 1.40 ATA, while for open-circuit SCUBA, the O2 fraction would never exceed 40% by volume or an O2 partial pressure of 1.40 ATA, whichever exposed divers to less O2.

One commenter (Ex. 6-2) responded to this proposed condition by stating, "The concept that diving with a higher concentration of [O2] than compressed air removes the risk of DCS is ludicrous. Any level of nitrogen predisposes individuals to the likelihood of DCS. * * * " The following comment submitted by Dr. Larry Raymond (Ex. 5-1), an occupational-health physician with experience in treating diving-related injuries, addressed this issue:

Oxygen-rich mixtures of nitrogen and oxygen ("Nitrox") have indeed been shown to be advantageous[] with regard to decompression sickness (DCS). Nitrox allows longer dives at a given depth (vs. air dives). Nitrox is [] safe, as long as meticulous care is given to gas mixing, lubrication of oxygen-exposed surfaces (avoid fire), and compliance with depth limits and decompression schedules.

Although the Agency believes that increased O2 levels can reduce the risk of DCS by displacing nitrogen in the nitrox breathing-gas mixture, it notes that the major purpose of this condition is to prevent O2 toxicity or hypoxia, not to remove the risk of DCS. Another commenter (Ex. 6-1), who had three years of experience with nitrox breathing-gas mixtures as a recovery diver and diving instructor, recommended that "any diver who is engaged in recreational diving with open-circuit [SCUBA], be supplied with a breathing gas consisting of a high percentage of oxygen mixed with nitrogen." This recommendation attests to the health and safety benefits of nitrox breathing-gas mixtures, as incorporated in the final rule.

OSHA is including this condition in the final rule as proposed because it finds that the minimal level of 22% is consistent with the minimal level required for nitrox breathing-gas mixtures.(4) Additionally, the Agency is including in the final rule the upper limits designated for the O2 component in the nitrox breathing-gas mixture as proposed (i.e., 40% by volume and 1.40 ATA). The 40% limit specifies the level above which equipment exposed to O2 (e.g., SCUBA cylinders, valves, first-stage regulators, high-pressure hoses) must be rated for O2 service because of the increased risk of an O2-accelerated explosion (Ex. 3-12, p. 15-18), while the 1.40-ATA limit represents the maximum level of O2 exposure that effectively will prevent O2 toxicity among divers (see Ex. 3-4, pp. 3-5 through 3-15 and P-37 through P-45, and Ex. 3-10).

4. Regulating O2 Exposures and Diving Depth

(a) Limiting O2 partial pressure. This proposed condition identified procedures for preventing O2 toxicity. Employers would have to: (i) Determine a diver's O2 exposure duration using the maximum partial-pressure O2 exposure during the dive and the total dive time (i.e., from the time the diver leaves the surface until the diver returns to the surface); and (ii) using the diver's exposure duration, ensure that a diver exposed to partial pressures of O2 between 0.60 and 1.40 ATA does not exceed the 24-hour single-exposure O2 limits specified by the 2001 NOAA Diving Manual (Ex. 3-12, p. 3-23) or by the 1995 Diving Science and Technology Corporation (DSAT) report contained in the publication entitled "Enriched Air Operations and Resource Guide" (Ex. 3-13, p. 34).

Under this condition, paragraph (i) reduces the risk of developing O2 toxicity by regulating O2 exposures according to increases in O2 partial pressure (i.e., dive depth) and dive duration. Paragraph (ii) controls O2 exposures by requiring that diving operations conform to the 24-hour single-exposure O2 limits specified in the 2001 NOAA Diving Manual and the 1995 DSAT report contained in the publication entitled "Enriched Air Operations and Resource Guide." In the single comment received on this proposed condition (Ex. 5-1), Dr. Raymond expressed concern about the deleterious effects of breathing O2 at 1.40 ATA, stating, "The risk of oxygen toxicity from Nitrox diving is a * * * very real concern. Oxygen-induced seizures usually abate when the high-oxygen gas * * * is replaced by air, but any seizure which occurs in the water is a potential disaster, placing the diver at risk for AGE, drowning and death." (Emphasis in original.)

As noted in the proposal, OSHA agrees that O2 toxicity is a substantial hazard to divers breathing nitrox breathing-gas mixtures. The Agency is retaining this condition in the final rule as proposed because the NOAA and DSAT procedures are designed to protect divers by effectively regulating their exposure to O2. Both NOAA and DSAT developed their O2-exposure limits using models and theories extensively tested in the field for safety and efficacy. The recreational diving industry recognizes and uses both of these procedures and, as OSHA concluded in granting the Dixie Diver variance, both of these procedures afford divers adequate protection against O2 toxicity. Moreover, restricting diving operations to 130 fsw (see Condition 4(b) below) will provide divers with added protection from O2 toxicity.

(b) Limiting diving depth. Under this proposed condition, employers would have to limit divers covered by the amendment to a maximum depth of 130 fsw or to a maximum O2 partial pressure of 1.40 ATA, whichever exposes them to less O2. OSHA is adopting the requirements specified by this proposed condition in the final rule because it finds that the condition limits divers' overall exposure to O2. In addition, as noted in the discussion of Condition 3 above, limiting the depth of diving operations also will restrict the partial pressure of oxygen in the nitrox breathing-gas mixture, thereby lowering the incidence of O2 toxicity.

5. Use of No-Decompression Limits

(a) No-decompression procedures. In the proposal, this condition specified that employers must ensure that divers using nitrox breathing-gas mixtures remain within the no-decompression limits specified for single and repetitive air diving. These limits are available in the 2001 NOAA Diving Manual (Ex. 3-12) or the 1994 DSAT report entitled "Development and Validation of No-Stop Decompression Procedures for Recreational Diving: The DSAT Recreational Dive Planner" (Ex. 3-14). In determining the no-decompression limits for nitrox breathing-gas mixtures in its 2001 Diving Manual, NOAA applies the equivalent-air-depth ("EAD") formula.

Divers using nitrox breathing-gas mixtures can use the EAD formula to determine accurately the no-decompression limits for different nitrogen partial pressures. According to NOAA, EAD "is the depth based on the partial pressure of nitrogen in the gas mixture to be breathed, rather than the actual depth of the dive" (Ex. 3-12, p. 15-7).

NOAA applies its EAD formula in determining what equivalent air-decompression limits to use with nitrox breathing-gas mixtures. The formula assumes that equivalent nitrogen partial pressures and dive durations will result in similar DCS risk to dives performed with air. OSHA believes that the NOAA EAD formula can accurately estimate the DCS risk associated with nitrox breathing-gas mixtures based on equivalent nitrogen partial pressures and dive durations used in air diving. In the proposal, OSHA cited comments regarding the efficacy of the EAD formula submitted to the record by Dr. Edward D. Thalmann (Ex. 2-7), a world-renowned expert in treating diving-related medical emergencies among recreational divers. In these comments, Dr. Thalmann asserts that research data show that the EAD approach is valid for computing no-decompression limits for O2 partial pressures as high as 1.5 ATA. He also stated that DCS associated with breathing a nitrox gas mixture "should not be substantially different in incidence and severity compared to diving on air[,] provided the Nitrox no-decompression times are computed from accepted air no-decompression limits using the [NOAA] EAD [formula]." Dr. Thalmann concluded that, within these constraints, "there is no rationale for having different requirements for * * * air and Nitrox no-decompression diving."

OSHA received two comments on the proposed condition. The first commenter (Ex. 6-4) stated:

Nitrox may reduce [DCS] only if you do not allow for more uptake[;] by staying longer you have just negated this aspect. [DCS] is not merely a subject of "coming up too fast,["] but rather [is caused by] "inadequate decompression." There is no miracle table/schedule and [DCS] can and will manifest regardless of the table, mix o