This entire discussion is exausting, and has been since padi said nitrox would kill you. Scuba is an unregulated industry so far. That means that you get interpretation from many different agencies outside of the scuba parameter, trying to apply rules for transport, and filling, and storage. A hodge podge of selective implementation at best.
Like everything else, do your own research and determine what makes sense to you and the people in your hood. This entire debate and the poor quality of the fill stations in my hood is what prompted me to bite the bullet and by my own compressor. In the USA it is really hard to seperate marketing, revenue generation, urban scuba myth, and reality. It is why you have had so many responses from differing angles.
Eric
The Scuba Industry is definitely 100% regulated. The enforcement of the regulations is lax, however, until a complaint or accident occurs. Cylinders for Scuba are specifically mentioned in Title 49 of the CFR (DOT). Additionally, if you have employees in the USA you must deal with OSHA. Furthermore, if you sell goods to customers, you have the UCC (Uniform Commercial Code) which varies state by state. Basically, if you have to provide a protection to your employees because it is deemed hazardous to do so, you must extend that protection to your customers too.
Again, please read the OSHA statutes for RECREATIONAL SCUBA MANDATORY REQUIREMENTS, I included the preamble to alleviate some confusion for those who have never read the standard:
http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=FEDERAL_REGISTER&p_id=18073
Recreational Scuba gets and exemption from the MANDATORY decompression chamber requirements as long as 4 conditions are met and that is the only exemption from the Commercial Diving Standard that they get. According to 1910.5, whenever terms like MUST, SHALL, REQUIRED, etc are used , they are MANDATORY LANGUAGE.
"(f) Compliance with other OSHA standards. Under this proposed condition, employers must ensure that SCUBA equipment in which either nitrox breathing-gas mixtures or pure O2 is under high pressure (i.e., exceeding 125 psi) complies with the requirements of paragraphs (i)(1) and (i)(2) of § 1910.430. OSHA is including this condition in the final standard as proposed because it ensures that this equipment is free of ignition sources that could cause an O2-accelerated explosion. As noted above in the discussion of Condition 3(d)(iii), the Agency believes that paragraphs (i)(1) and (i)(2) of § 1910.430 reduce this risk by requiring employers to use diving equipment designed for O2 service and to clean the equipment of flammable materials before such use.(7)"
"Footnote 7 In addition, employers already are required to comply with other OSHA standards that provide for accurate mixing and decontamination (especially hydrocarbon removal) of breathing gases, and they must assure that employees are properly protected during these activities. These standards include the appropriate provisions of §§ 1910.101 ("Compressed gases (general requirements)"), 1910.169 ("Air receivers"), and 1910.134 ("Respiratory protection").
While umbilicals, helmets, hoses, 2nd stages, and other low pressure systems subjected to less than 125psi do not need to be cleaned when they encounter less than 40% O2, High pressure components MUST be cleaned. You can't extend 40% to everything which it seems some folks have. It is important to read the WHOLE standard and not pick piecemeal from it. Additionally, directly from Condition 6 of the standard:
(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.
You will be able to find manufacturers who will give letters of compliance so you can use a membrane system. I have personally not been able to find a manufacturer to supply such a required letter for a continuous flow system though. The mixing process begins with about 100% O2 and then is diluted in the mixing stick before being pumped through the compressor. Equipment failure, design errors, operator errors, etc can and do happen which could lead to a catastrophic failure of a compressor and possibly cause injury or worse when using such systems in such a manner.
If you are using a continuous flow system without meeting all of the requirements, you are in violation of the standard. I wouldn't want to be in your shoes if an accident happens!!
"(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%"
You can use one on an oil-less or oil-free compressor, but not an oil-filled.
Regardless of how you mix your gas, you still need to clean cylinders at 23.5%. 1910.1200 defines an OXIDIZER at 23.5%. DOT REQUIRES cleaning at 23.5%. From 1910.430:
1910.430(e)
Compressed gas cylinders. Compressed gas cylinders shall:
1910.430(e)(1)
Be designed, constructed and maintained in accordance with the applicable provisions of 29 CFR 1910.101 and 1910.169 through 1910.171.
From 1910.101:
1910.101(a) "Inspection of compressed gas cylinders." Each employer shall determine that compressed gas cylinders under his control are in a safe condition to the extent that this can be determined by visual inspection. Visual and other inspections shall be conducted as prescribed in the Hazardous Materials Regulations of the Department of Transportation (49 CFR parts 171-179 and 14 CFR part 103). Where those regulations are not applicable, visual and other inspections shall be conducted in accordance with Compressed Gas Association Pamphlets C-6-1968 and C-8-1962, which is incorporated by reference as specified in Sec. 1910.6. From the links I provided in my 1st post 173.302b requires cleaning at 23.5%. Directly from the Offilcal DOT Interpretation: Q1: If a cylinder is to be used to transport Nitrox, at what Oxygen percentage must a cylinder used for Oxygen service be cleaned and must the cylinder cleaning conform to the cleanliness standards specified in 173.302? A1: Gas mixtures with Oxygen concentrations greater than 23.5% by volume should be considered to cause or contribute to combustion of other material to a greater extent than air. These gas mixtures must be described as "Compressed gas, oxidizing, n.o.s." and must be classified and labeled with a Division 2.2 (nonflammable gas) primary hazard and a Division 5.1 (oxidizer) subsidiary hazard. If the Oxygen concentration is greater than 23.5%, the conditions specified in § 173.302(b) must be met. Good luck with all of this gentlemen. I know we all mean well and are trying to do the right thing. Ask the right questions of those in charge of the regulations and you will get to the bottom of it. I have been a dive professional for some time and it took quite a bit of time and training to find this knowledge. Please don't shoot the messenger for the message. So many people have so many opinions but at crunch time, it is the one with the fine book and regulations who will cost you. I encourage everyone to attend the DOT training when it is available and to ask questions of the regulatory authorities as they are the AUTHORITIES. Best Wishes |