Storage

1. Store gas cylinders in a location that is dry, cool, well-ventilated, away from combustible materials, and protected from weather. This prevents or mitigates damage from environmental factors.
2. Ensure that incompatible gases (i.e., oxidizer and flammable gas) are segregated.
3. Restrain each gas cylinder per the following:
   • Medium and large sized cylinders (> 18” tall)
     • Restrain each cylinder with two non-combustible (steel or aluminum) chains placed at one third and two thirds of the way up from the base.
     • The chains shall either be bolted securely to a wall, attached to a steel cylinder rack which itself is bolted to the wall or the floor, or they shall be bolted to a steel cabinet which itself is bolted to the wall or the floor (Figure 1).
     • At no point shall cylinders be chained to movable furniture such as tables, wooden cabinets, or any other combustible item.
   • Small cylinders (< 18” tall)
     • Double chaining is not always practical. A single chain may be used provided the chain is noncombustible (steel or aluminum) and the chain is affixed to the wall or floor, or to a steel cabinet which is itself affixed to the wall or floor.
     • Place the chain in such a way that is sufficient to prevent the cylinder from falling or escaping in the event it is knocked or shaken (Figure 2).
   • Lecture bottles
     • Clamp the lecture bottle to a rigid structure (e.g., lab lattice) when in use.
     • Store lecture bottles such that they can’t fall or escape. They do not, however, require individual restraint in storage.
4. Fit gas cylinders in storage with caps to protect valve stems from damage (Figure 3). According to 8 CCR §4650, “All cylinders which are designed to accept valve protection devices [protective cap] shall be equipped with such devices when the cylinders are not in use or connected for use.”
   • NOTE: Certain cylinders are not designed to be fitted with a protective cap. This is often the case for some small cylinders or relatively low-pressure cylinders.

The above represent basic requirements for proper gas cylinder storage – see the Compressed Gas Cylinder Storage Fact Sheet for more information. However, certain hazardous gases (e.g., toxic, reactive, or corrosive) have stricter storage requirements.

• Oxygen. 8 CCR §4650 states, “Oxygen cylinders in storage shall be separated from fuel gas cylinders or combustible materials (especially oil or grease) a minimum distance of 20 feet or by a non-combustible barrier at least 5 feet high, or a minimum of 18 inches (46 centimeters) above the tallest cylinder and having a fire-resistance rating of at least one hour.”
• Toxic or corrosive gases may have special safety requirements, including cross purging facilities.
• Pyrophoric (phosphine, arsine, diborane, silane, germane etc.) and highly toxic gases (e.g. phosphine, arsine) must be stored and used in enclosed, exhausted cabinets equipped with alarms.
• Time-Sensitive Gas Cylinders: 1,3-Butadiene, Hydrogen Fluoride, Hydrogen Bromide.
  • Butadiene may undergo hazardous autocatalytic polymerization in cylinders, and the risk increases with storage time. If an old butadiene cylinder is discovered, do not attempt to move. Restrict access and call HazMat at (323) 442-2200. Refer to the Time Sensitive Chemicals web portal and Peroxide Formers Guidance Spreadsheet (“Basic Info”, “Flowcharts” and “Class A” tabs) for more information, including expiration dates.
  • Steel cylinders of anhydrous hydrogen fluoride and hydrogen bromide may develop a dangerous internal pressure of hydrogen if stored for an excessive time. The hydrogen, which arises from slow reaction of the HF or HBr with iron, is on record as having caused over-pressurization and spontaneous explosion of over-age cylinders, an extremely dangerous occurrence. If a hydrogen fluoride or hydrogen bromide cylinder of uncertain history is discovered, do not attempt to move. Restrict access and call HazMat at (323) 442-2200. Refer to the EH&S Other Time Sensitive Chemicals webpage for detailed guidance.

Transport

1. Before transporting compressed gas cylinders, ensure that safety caps are in place.
2. Employ wheeled carts to transport compressed gas cylinders and ensure that cylinders are securely fastened. DO NOT exceed the capacity of the cart.
3. Avoid moving or transporting large, compressed gas cylinders great distances by rolling them on their ends (“milk churn”) as this can be dangerous. This method may be used over a short distance within rooms and only by trained personnel.
4. Use a freight elevator to move gas cylinders between floors. If a freight elevator is not available, a passenger elevator may be used.
5. Individuals are permitted to ride in elevators while transporting a gas cylinder provided that the compressed gas is non-toxic.
6. If toxic gases or cryogenic liquids are being transported, individuals shall be prevented from entering the elevator while transporting the cylinder. Use signage that reads “Hazardous Materials Transport: No Entry” or similar language.
   • EH&S recommends transporting these gases between floors with two people: one person loads the cylinder on the initial floor and a second person receives it at the destination. It is important to note that this restriction also applies to vendors who are delivering these types of cylinders on campus.
   • Note that cryogenic materials continually off-gas. Any spillage can result in rapid boiling that can quickly and easily displace oxygen. In a small, enclosed space such as an elevator, this will become a low oxygen environment that may result in asphyxiation.
   • It only takes one to two breaths in a severely oxygen-deficient atmosphere (around 10%-13% oxygen) to experience sudden unconsciousness. Brain damage and death can occur rapidly thereafter.
7. Dry ice (frozen carbon dioxide) can pose similar hazards during transport on elevators, but the risk is somewhat mitigated versus liquid cryogens as dry ice sublimes more slowly than cryogens boil.
   • Minor (≤1 kg) quantities of dry ice in an insulated container may be transported in an occupied elevator with care; however, stairs are recommended.
   • Larger quantities shall be transported via stairs or an unoccupied elevator, with precautions (e.g., signage as described above) to prevent people from entering if the doors open on an intervening floor.
8. Dry ice baths containing solvent shall NOT be transported in elevators under any circumstances, as these mixtures evaporate much faster than pure dry ice in the event of spillage.

For more information on gases which are classified as simple asphyxiants, as well as the hazards posed by carbon dioxide, consult the following: Simple Asphyxiants and Carbon Dioxide: Hazards, Risk Assessment, and Mitigation and Simple Asphyxiants and Carbon Dioxide SOP.