What is the quality of your Oxygen? Our Oxygen meets a mil-spec standard known as Aviators Breathing Oxygen (MIL-0-2721OD) and is required to be 99.5 percent pure. The water vapor content must not be more than 7 ppm with a dew point of -81°F. The very low moisture content required of ABO is to ensure proper operation of the airplane oxygen system at the extremely low temperatures encountered during flight. Our oxygen consistently tests at 100% as delivered to us from our supplier. However as we transfill the ABO into customer cylinders there will be small amounts of other breathing gases introduced from the plumbing of the boosters and fill whips. Particularly where the cylinder being filled is small, the final content should be considered slightly less than 100%. For the purposes of setting dive computers or decompression software, we recommend using a value of 99% for the actual purity. What is the quality of your Helium? There is no widely recognized gas purity standard for Helium. We purchase a highly refined grade of Helium our specialty gas supplier calls Ultra High Purity, which they define to be 99.999% pure. Similar purity specifications from other gas suppliers are termed Laser Grade, Zero Grade or Semi-Conductor Grade. This level of purity is sometimes referred to with the generic term "five nines pure". According to our gas supplier, the price of Ultra High Purity Helium is about double the price of what are known as industrial, welding and balloon grades of Helium. We chose not to use those lesser grades of helium because they are commonly contaminated with methane, nitrogen, and sometimes with argon. Cylinder Contents & Labeling How can I be certain about my cylinder contents? We have a simple but effective system to assure you know what is in your cylinder. A work order tag is placed on the cylinder to indicate the desired final contents and pressure. The work order tag provides the fill station operator with a clear visual indication of what gas to put in the cylinder. Once the cylinder is filled, we assist you in performing an analysis of the cylinder contents in your presence. Finally, we affix a strip of biodegradable non-residue adhesive "tank tape" marked with your analysis. This is true for all Air, Nitrox, Trimix and Oxygen fills. What cylinder contents labels do you recommend? Unlabeled cylinders are assumed to contain air. For cylinders containing a gas other than air, our recommendations differ depending upon the intended use and type of gas. In sport diving, we recommend cylinders containing Nitrox with oxygen concentrations of 40% or less should be labeled with a color-coded, 6-inch-wide band. The top 1 inch and the bottom 1 inch of the band should be yellow. The middle of the band should be green with the word Nitrox in yellow. In technical diving, the cylinder labeling has become somewhat controversial with some training agencies specifically recommending against contents labeling and others requiring contents labeling. If you choose to label your cylinders, we recommend the following: Cylinders containing Nitrox less than or equal to 40% should be labeled with the words Nitrox or Breathing Gas Other Than Air. Cylinders containing Nitrox between 41% and 74% should be labeled with the words Decompression Mix or Breathing Gas Other Than Air. Cylinders containing oxygen concentrations of 75% or greater should be labeled with the word Oxygen. Cylinders containing Trimix should be labeled with the word Trimix or Breathing Gas Other Than Air. Cylinders containing Argon should be labeled with the word Argon AND the words DO NOT BREATHE. All cylinders containing a breathing gas other than air should have a label or tag indicating the oxygen percentage currently in the cylinder and the maximum operating depth (MOD). In addition, cylinders containing mixtures with MODs less than 100 feet should have the MOD marked in 3-inch-high numbers such that the MOD is clearly visible during the dive. What cylinder contents labels do you require? We think labels and stickers on SCUBA cylinders are in some ways counter productive because they encourage and obscure corrosion. We require all cylinders containing a breathing gas other than air to have a label or tag indicating the oxygen percentage currently in the cylinder. We require Argon cylinders to be clearly marked with the words DO NOT BREATHE. What cylinder contents labels do you obey? Filling a cylinder with a breathing gas other than is labeled can create dangerous situations where the contents might be used under the assumption it's actual contents match the labeling. If a cylinder has been dedicated to a specific breathing gas with permanent MOD or contents labels, we will fill that cylinder only with the labeled gas. For example, if the cylinder is labeled "Oxygen 20 ft" we will fill only with 100% Oxygen or if the cylinder is labeled with "70" maximum operating depth we will fill only with 50% Oxygen. If you wish a fill with other than the permanent contents label, the label must be removed or obscured (i.e. covered with tape). Do you sell Air? Yes, but we call it Normoxic Nitrox (also known as Oxygen-Compatible Air). We use the same oxygen-compatible compressors, filters, and gas-handling procedures to make our Air as we do our oxygen-enriched Nitrox mixtures. Our Air and Nitrox both meet the same Ultra Pure quality standards. Although the CGA G-7.1 standard for Grade "E" Air states that it may contain from 20% to 22% Oxygen, Air is normally expected to have 20.95% Oxygen content. Because our Air travels through some of the same plumbing as our other gases, it may analyze as high as 22% Oxygen content. Because of the chance that we might accidentally introduce Nitrox into an Air cylinder, we handle all cylinder fills with the same procedures. This means that we analyze our Air fills for Oxygen content in the same manner as we do our other breathing gas fills. The price for our Ultra Pure Oxygen-Compatible Air is the same as that of our other sport Nitrox Premixes. Oxygen Service What do Nitrox Ready and Oxygen Service mean? When the SCUBA diving community prepares an item for use with breathing gases containing high oxygen percentages or pure oxygen, they generally think in terms of washing it with detergents, replacing rubber parts such as O-rings and seals with oxygen-compatible equivalents and reassembling with oxygen-compatible lubricants. However, most other industries working with very high pressure oxygen have a very different standard known as oxygen service. Oxygen service means the materials are both: Oxygen Compatible -- compatible with high concentrations of oxygen. Oxygen Clean -- free of hydrocarbon contamination and particulate matter. True oxygen cleaning of an oxygen compatible component (often made from exotic metal alloys or other compounds) takes place in a special clean room, whose atmosphere is free of dust and contaminants. Once the component is free of hydrocarbons and other combustible elements, it is sealed within a sterile environment and never again exposed to normal atmospheric dust, moisture, and contaminants. Only then is the item said to be suitable for oxygen service. Some manufacturers offer diving products labeled Nitrox Ready, whose oxygen-compatible components are free of hydrocarbons and other flammable contaminants. The metal components are usually stainless steel or brass, which are suitable for use with oxygen at the pressures encountered in diving activities. The lubricant used in assembly is Christo-Lube® or other oxygen-compatible lubricants. The O-rings are made from Viton® or other oxygen-compatible materials. These components are not, however, assembled in a clean room or sealed in a sterile environment. As a result, the manufacturers do not label the products as suitable for oxygen service, although many divers consider them to meet oxygen service criteria at pressures encountered in the diving community. How do I get my cylinder and valve to be Nitrox Ready? Most cylinders and valves that have been in use have some level of hydrocarbon contamination. To make a cylinder and valve suitable for nitrox service, they must be disassembled and cleaned of hydrocarbon contamination and reassembled with oxygen-compatible O-rings and lubricant. This process requires training, special materials and is time-consuming. For a very reasonable fee, Fill Express can prepare your cylinder and valve for nitrox service. New cylinders and valves purchased from Fill Express are always prepared by the factory for nitrox service using facilities not available to local dive shops, these new cylinders and valves will never be any cleaner than the day they are put into service. How do I know that my cylinder and valve are Nitrox Ready? Once a cylinder and valve have been prepared for nitrox service, a special sticker (or often a special version of the evidence of visual inspection sticker) is affixed to the cylinder. Unless the sticker explicitly states that a cylinder and valve are suitable for nitrox service, they are not. If the cylinder is ever filled with anything other than Oxygen compatible breathing gases, it is no longer suitable for nitrox service, and the sticker should be removed. Even with the best quality fills, hydrocarbon contamination can build up over time. Fill Express recommends that the cylinder and valve should be prepared for nitrox service each time the cylinder is hydrostatically tested. What does the large green and yellow Nitrox decal mean? Per PSI standards, presence of a color-coded 6-inch-wide green and yellow NITROX band decal indicates only that the cylinder contents are Nitrox. The large NITROX band does not indicate the cleanliness of the cylinder, its suitability for partial pressure blending, or what method was used to fill the cylinder. It is only the evidence of inspection sticker that indicates if a cylinder and valve are Nitrox Ready. When does my cylinder or valve need to be Nitrox Ready? The recreational diving industry has widely followed what is often referred to as the "40% Rule" which states the cylinder and valve must be Nitrox Ready only when they will be exposed to a gas mixture containing more than 40% oxygen. While sport diving Nitrox and technical diving Trimix don't absolutely require that the cylinder and valve be Nitrox Ready, many fill stations blend directly in the tank by first adding 100% oxygen and then topping off with oxygen compatible air. This process, known as partial-pressure blending, requires that the cylinder and valve be Nitrox Ready. In practice, almost all Nitrox and Trimix cylinders are Nitrox Ready because partial-pressure filling is so common. You should keep in mind that not everyone agrees with the 40% rule. Luxfer has an extremely detailed statement of their position on aluminum cylinders and oxygen which argues any cylinder that contacts more than 23.5% should be oxygen clean.