Recently, an LBNL investigator created several "custom mixtures" of gases in his laboratory to support the research he was conducting. This was done by transferring gases from one or more cylinders to another at high pressures - a process known as "trans-filling". The practice of mixing gases in commercial DOT cylinders (i.e., the type which are obtained from gas vendors such as Matheson, Scott and AirGas) raises several serious safety issues as illustrated below.

• Manually transferring high-pressure gases creates a potentially dangerous physical hazard in the laboratory. Tremendous amounts of stored energy can be released during component failures and line ruptures. These are often the result of using inappropriate or non-high pressure-rated tubing, fittings and connections. Ordinary fittings cannot withstand typical gas cylinder pressures of 1500 psi or more and could fail, resulting in the release of energy and toxic and/or hazardous gases.
• Another safety concern pertains to the inherent hazard of the gases being used. One of the gas mixtures made by the researcher was 5% silane in helium. Silane is a pyrophoric gas, (i.e., it spontaneously ignites upon exposure to air). A mishap (such as a rupture) during trans-filling could have had disastrous results.
• Waste disposal is another problematic area. The researcher who made the mixtures has left the Laboratory. Makeshift labels were applied, but some fell off the cylinders. Therefore, the gases were unidentifiable, couldn’t be used, and had to be disposed of as hazardous waste. However, to properly handle, transport, and dispose of the cylinders, they needed to be sampled and analyzed. LBNL doesn’t have facilities or qualified personnel to sample and analyze unknown gases, so an external environmental consultant had to be hired at considerable cost.
• Trans-filling is also a safety and compliance issue with OSHA. OSHA requires that trans-filling be done only by the gas manufacturer using qualified, trained personnel with appropriate equipment and operational procedures.

Laboratory personnel should obtain "custom" gas mixtures only through approved sources. The Procurement Department has established service agreements with two gas supply vendors: Scott Specialty Gases and AirGas. All gas purchases should be through these suppliers. Custom gas mixtures, pure gases, semi-conductor gases, calibration standards and unique gases can be obtained from Scott Specialty Gases. (AirGas is normally used for inert gases and industrial gases.) Both vendors will deliver cylinders to the work area and will also pick up empty cylinders.

The Laboratory has established procedures for the purchase and use of toxic, pyrophoric, corrosive and other hazardous gases. These gases must be reviewed and approved by an EH&S industrial hygienist prior to purchase. This is explained further in the Procurement Department’s web-page (http://Purch1.lbl.gov/lbnl/scott.htm). Depending on the type of gas and its inherent hazards, engineering controls such as ventilation, gas detection and/or alarm systems may be needed. These are further discussed in PUB 3000, Chapter 13, "Gases" (/ehs/pub3000/CH13.html.) Users must also be trained. At a minimum, Compressed Gas Safety (EHS 231) and Chemical Hygiene and Safety Training (EHS 348) are required. On line registration for these courses may be done at the EH&S Training Web Site, (/ehs/html/training.htm).

If the Laboratory’s gas vendors are not able to provide you with the gases you require, if you have any questions about pressure safety or the use of hazardous gases, or if you have a special need, please contact John Seabury of the EH&S Division’s Field Support Department at extension 6547 for assistance.