Recreational diving instructor conditions

Under 1910.401(a)(3) and Appendix C, yes — an employer may omit a decompression chamber if they comply with all the conditions in Appendix C. Appendix C to Subpart T of Part 1910 lays out mandatory alternative conditions that, when fully met, allow employers of recreational diving instructors and guides not to provide a decompression chamber otherwise required by 1910.423(b)(2), 1910.423(c)(3), or 1910.426(b)(1). See 1910.401(a)(3) and Appendix C to Subpart T (Alternative Conditions).

Under Appendix C to Subpart T, the employer must ensure each employee operates the rebreather according to the rebreather manufacturer's instructions. That means following the manufacturer's procedures for use, maintenance, sensors, and alarms (e.g., moisture traps and CO2/ O2 sensors) for every device before and during diving operations. See Appendix C to Subpart T and 1910.401(a)(3).

Under Appendix C to Subpart T, the employer must ensure each rebreather has a counterlung with enough breathing-gas volume for the diver’s respiration rate and includes a baffle system and/or moisture-separating system that keeps moisture out of the scrubber. This helps prevent scrubber degradation and CO2 retention. See Appendix C to Subpart T and 1910.401(a)(3).

Under Appendix C to Subpart T, an employer may place a moisture trap in the breathing loop only if the rebreather manufacturer approves both the moisture trap and its location, and each employee uses the trap according to the manufacturer's instructions. Employer compliance requires documented manufacturer approval and user procedures. See Appendix C to Subpart T and 1910.401(a)(3).

Under Appendix C to Subpart T, each rebreather must have a continuously functioning moisture sensor connected to a visual or auditory alarm that the diver can readily detect under the diving conditions, and the sensor must warn in time for the diver to terminate the dive and return safely. Divers must use the moisture sensor per the manufacturer's instructions. See Appendix C to Subpart T and 1910.401(a)(3).

Under Appendix C to Subpart T, each rebreather must contain a continuously functioning CO2 sensor in the breathing loop, with the sensor’s location approved by the manufacturer, integrated with a visual or auditory alarm that is readily detectable by the diver, and the alarm must remain continuously activated when inhaled CO2 reaches or exceeds 0.005 atmospheres absolute (ATA). See Appendix C to Subpart T and 1910.401(a)(3).

Under Appendix C to Subpart T, employers must calibrate CO2 sensors before each day's diving operations (and more often if necessary) according to the sensor manufacturer's instructions using equipment and procedures accurate to within 10% of a CO2 concentration of 0.005 ATA or less. The calibration must maintain that accuracy and be verified to be within 10% of 0.005 ATA. See Appendix C to Subpart T and 1910.401(a)(3).

Under Appendix C to Subpart T, an employer may use a manufacturer-developed schedule for replacing CO2-sorbent material as an alternative to a continuously functioning CO2 sensor only if the schedule is developed according to the canister-testing protocol in Condition 11 of Appendix C and the scrubber canister is used within the temperature range covered by those tests (or the manufacturer extends the protocol to other temperatures). See Appendix C to Subpart T (Condition 1(h) and Condition 11) and 1910.401(a)(3).

Under Appendix C to Subpart T, when using CO2-sorbent replacement schedules an employer must ensure each rebreather uses a commercially manufactured, disposable scrubber cartridge that is approved by the rebreather manufacturer, removes CO2 from exhaled gas, and keeps inhaled CO2 below a partial pressure of 0.01 ATA. Employers must follow the manufacturer's approval and use instructions. See Appendix C to Subpart T (Condition 1(i)) and 1910.401(a)(3).

Under Appendix C to Subpart T, an employer may manually fill scrubber cartridges only if the rebreather manufacturer permits manual filling, the employer fills them per the manufacturer's instructions, uses a replacement schedule developed under the appendix, and demonstrates that the manual filling meets the appendix requirements. Employer documentation and adherence to the manufacturer's procedures are required. See Appendix C to Subpart T (Condition 1(j)) and 1910.401(a)(3).

Under Appendix C to Subpart T, the information module must (1) warn of solenoid failures and other electrical weaknesses (visual or auditory), (2) for semi-closed rebreathers provide a visual display for CO2 partial pressure or deviations around a preset CO2 partial pressure of 0.005 ATA, and (3) for closed-circuit rebreathers display partial pressures of O2 and CO2 (or deviations around preset CO2 at 0.005 ATA and O2 at 1.40 ATA or lower), breathing-loop gas temperature, and water temperature. See Appendix C to Subpart T (Condition 1(k)) and 1910.401(a)(3).

Under Appendix C to Subpart T, employers must ensure, before each day's diving operations (and more often as needed), that the electrical power supply and electrical/electronic circuits in each rebreather operate as required by the rebreather manufacturer's instructions. This includes batteries, solenoids, and information-module electronics. See Appendix C to Subpart T (Condition 1(l)) and 1910.401(a)(3).

Under Appendix C to Subpart T, closed-circuit rebreathers must have supply-pressure sensors for O2 and diluent gases, continuously functioning temperature sensors for the inhalation side of the gas loop and ambient water, at least two functioning, temperature-compensated O2 sensors located in the inhalation side (manufacturer-approved), a gas-controller package with electrically operated solenoid O2-supply valves, a pressure-activated regulator with a second-stage diluent addition valve, a manual gas-supply bypass valve, and separate O2 and diluent cylinders. See Appendix C to Subpart T (Section 2) and 1910.401(a)(3).

Under Appendix C to Subpart T, employers must calibrate O2 sensors before each day's diving operations (and more often when necessary) per the sensor manufacturer's instructions using equipment and procedures accurate to within 1% of the O2 fraction by volume; sensors must be accurate to within 1% of the O2 fraction, and employers must replace sensors that fail to meet that 1% accuracy. See Appendix C to Subpart T (Section 2(c)) and 1910.401(a)(3).

Under Appendix C to Subpart T, the employer must ensure nitrox O2 fraction exceeds the fraction in compressed air (i.e., >22% by volume); for open-circuit SCUBA nitrox must not exceed 40% O2 or an O2 partial pressure of 1.40 ATA—whichever presents less O2 exposure; and for rebreathers O2 partial pressure must never exceed 1.40 ATA. See Appendix C to Subpart T (Section 3) and 1910.401(a)(3).

Under Appendix C to Subpart T, employers must ensure each diver’s exposure to O2 partial pressures between 0.60 and 1.40 ATA does not exceed the 24-hour single-exposure limits in either the 2001 NOAA Diving Manual or the 1995 DSAT Oxygen Exposure Table; determine exposure using the dive's maximum O2 partial pressure and total dive time; and ensure no diver exceeds 130 feet of sea water (fsw) or a maximum O2 partial pressure of 1.40 ATA, whichever exposes the diver to less O2. See Appendix C to Subpart T (Section 4) and 1910.401(a)(3).

Under Appendix C to Subpart T, for nitrox diving the employer must ensure divers remain within the no-decompression limits published for single and repetitive air diving in the 2001 NOAA Diving Manual or the 1994 DSAT No-Decompression Tables; employers may also allow dive-computers that use those same no-decompression limits and provide reliable output reflecting them. See Appendix C to Subpart T (Section 5) and 1910.401(a)(3).

Under Appendix C to Subpart T, employers must have properly trained personnel mix nitrox breathing gases, use nitrogen as the only inert gas, and mix the breathing gas before filling cylinders using continuous-flow or partial-pressure mixing techniques specified in the 2001 NOAA Diving Manual or a filter-membrane system. See Appendix C to Subpart T (Section 6(a)) and 1910.401(a)(3).

Under Appendix C to Subpart T, employers must determine the O2 fraction of breathing-gas mixtures before each day's diving operations using an O2 analyzer that is accurate to within 1% of the O2 fraction by volume and maintain that accuracy per the analyzer manufacturer's requirements. See Appendix C to Subpart T (Section 6(b)) and 1910.401(a)(3).

Under Appendix C to Subpart T, when breathing gas is commercially supplied nitrox, the employer must ensure the O2 meets CGA G-4.3-2000 specifications (or equivalent aviator specs) and the commercial supplier must determine O2 fraction with an analytic method accurate to within 1% while the mixture is in the charged tank, and include documentation of the O2-analysis procedures and the O2 fraction when delivering charged tanks to the employer. See Appendix C to Subpart T (Section 6(b) & 6(c)) and 1910.401(a)(3).

Under Appendix C to Subpart T, before producing nitrox mixtures using a compressor where any system component exceeds 125 psi, the compressor manufacturer must document suitability for mixing high-pressure air with the highest O2 fraction used; the employer must comply with Appendix C paragraph 6(e) unless the compressor is rated for O2 service and is oil-less/oil-free; and if the highest O2 fraction used in mixing exceeds 40%, the employer must ensure the compressor meets the requirements in 1910.430(i)(1) and 1910.430(i)(2). See Appendix C to Subpart T (Section 6(d)) and 1910.401(a)(3).

The compressor manufacturer must provide documentation that the compressor is suitable for mixing the high‑pressure air with the highest oxygen fraction used in the nitrox breathing‑gas mixture when operated according to the manufacturer's operating and maintenance specifications. See the requirement in 29 CFR 1910 Subpart T Appendix C and the related O2‑service rules in 1910.430(i)(1) and (i)(2).

The employer must filter the high‑pressure air to produce O2‑compatible air and obtain documentation from the filter‑system manufacturer that the filter system is suitable for producing O2‑compatible air when operated per the manufacturer's operating and maintenance specifications. This is stated in 29 CFR 1910 Subpart T Appendix C.

Yes. The employer must continuously monitor the air downstream from the filter for hydrocarbon contamination. This continuous monitoring requirement is in 29 CFR 1910 Subpart T Appendix C.

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

The employer must ensure the equipment contains (or incorporates) an open‑circuit emergency‑egress ("bail‑out") system in which the second stage of the regulator connects to a separate supply of emergency breathing gas, and that the emergency breathing gas consists of air or the same nitrox mixture used during the dive. This bail‑out requirement is in 29 CFR 1910 Subpart T Appendix C.

As an alternative to the bail‑out system in the Appendix, the employer may use: (1) for open‑circuit SCUBA, an emergency‑egress system as specified in [1910.424(c)(4)], or (2) for semi‑closed and closed‑circuit rebreathers, a system configured so the second stage of the regulator connects to a reserve supply of emergency breathing gas. See 29 CFR 1910 Subpart T Appendix C and the alternative in 1910.424(c)(4).

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. This manufacturer‑information requirement is in 29 CFR 1910 Subpart T Appendix C.

Before each day's diving operations, the employer must verify that a hospital, qualified health‑care professionals, and the nearest Coast Guard Coordination Center (or equivalent rescue service) are available to treat diving‑related medical emergencies. The employer must also ensure the dive site has a means to alert those resources in a timely manner and that transportation to a decompression chamber is available when none is on site, able to deliver the injured diver to the chamber within four hours travel time. See 29 CFR 1910 Subpart T Appendix C.

The employer must ensure portable O2 equipment is available that delivers medical‑grade oxygen meeting the medical USP oxygen (Type I, Quality Verification Level A) requirement of CGA G‑4.3‑2000, delivers it to a transparent mask covering the injured diver's nose and mouth, and provides sufficient O2 from recognition of symptoms until the injured diver reaches a decompression chamber. See 29 CFR 1910 Subpart T Appendix C.

Before each day's diving operations, the employer must ensure that at least two attendants, employees or non‑employees, qualified in first aid and administering O2 treatment are available at the dive site, and the employer must verify their qualifications. See 29 CFR 1910 Subpart T Appendix C.

The employer must designate an employee or non‑employee to make entries in the diving log and verify that the designee understands diving and medical terminology and proper procedures to make correct log entries. The diving log must conform to the record‑of‑dive requirements in [1910.423(d)], and records must be maintained per [1910.440]. See 1910.423(d) and 1910.440.

Yes. The employer must ensure that a hard‑copy of the no‑decompression tables used for the dives is readily available at the dive site whether or not divers use dive‑decompression computers. See 29 CFR 1910 Subpart T Appendix C.

Each diver must receive training that enables safe and effective performance while using open‑circuit SCUBA or rebreathers supplied with nitrox mixtures, and must be able to demonstrate critical tasks including recognizing excessive CO2 and O2, taking appropriate action when detected, and properly evaluating, operating, and maintaining their diving equipment under encountered conditions. See 29 CFR 1910 Subpart T Appendix C and the general employee training duty in 1910.401.

The employer must ensure the rebreather manufacturer used the North Atlantic Treaty Organization (NATO) CO2 absorbent‑activity test, the RoTap shaker and nested‑sieves test, the Navy Experimental Diving Unit (NEDU)‑derived Schlegel test, and the NEDU MeshFit software to determine that the CO2‑sorbent material meets the manufacturer's specifications. These testing requirements are in 29 CFR 1910 Subpart T Appendix C.

The employer must ensure canister testing uses the specified ventilation rates and parameters in Table I: 22.5 Lpm (tidal volume 1.5 L, 15 breaths/min, CO2 injection 0.90 Lpm); 40.0 Lpm (2.0 L, 20 breaths/min, CO2 1.35 Lpm); and 62.5 Lpm (2.5 L, 25 breaths/min, CO2 2.25 Lpm). These parameters are in 29 CFR 1910 Subpart T Appendix C.

Canister duration testing must use a minimum of four water temperatures (40, 50, 70, and 90 °F), perform at least eight trials at each combination of temperature and ventilation/CO2 rates, keep temperature variation limits between trials, use the average of the eight trials in the analysis, analyze results with the repeated‑measures statistics described in NEDU Report 2‑99, and specify replacement schedules using the lower prediction line of the 95% confidence interval without extrapolation beyond tested conditions. See 29 CFR 1910 Subpart T Appendix C.

Yes. The employer must ensure the breathing‑gas temperature is monitored at the rebreather mouthpiece (the "chrome T" connector) and that this temperature conforms to the temperature of a diver's exhaled breath at the water temperature and ventilation rate used during the trial. See 29 CFR 1910 Subpart T Appendix C.