A diver brought in a set of doubles for a nitrox fill. When I told him I wouldn't fill the tanks without all the proper markings (i.e., a nitrox tank band) he told me "there's no rule" mandating the tank bands. He's both right and wrong. There is no specific law, but there are both regulations and precedents to consider.
The first rule is simple. It is our store policy. We want the tanks marked appropriately. We are under no obligation to fill any cylinder, nitrox or air. We do so by choice. If we have concerns over safety, we do not fill.
There are requirements under OSHA rules that do apply to the persons filling the tanks. Businesses are required to provide "a workplace free from serious recognized hazards and comply with standards, rules and regulations issued under the OSHA Act.." As part of that requirement we have to ensure that our emplyees are aware of the contents of any cylinders in their care. Because of the inherent hazards in dealing with a gas mixture of elevated oxygen content our employees must be made aware of the specific gas containd in the cylinders. We accomplish this through the use of proper cylinder markings.
Further, the Code of Federal Regulations (CFR) chapter 29 CFR 1910.101(b) requires that cylinders be marked according to compressed Gas Association (CGA) requirements. A self checklist for gas handling includes the following question:
"Do all compressed gas cylinders have their contents and
precautionary labeling clearly marked on their exteriors?
[29 CFR 1910.101(b)]"
The third factor in deciding if markings are required is what is often called an "industry standard." In the even of an accident, the investigation includes determining if there is an industry standard of operation and how that standard would apply. Since all training agencies require proper cylinder marking including a tank band it would be very difficult to defend filling a cylinder with nitrox that did not have such markings.
There are many stores that will fill any tank with nitrox, marked or not. That is a decision for each store to make. I choose for Diving Enterprises to protect the health and safety of our employess and customers. The price of a nitrox fill is no excuse to endangering any person.