Management of Pressurized Gas Cylinders

Date: Oct. 21, 2019
Version: 01

Purpose

To provide guidance to departments, principal investigators (PIs), and workplace supervisors regarding purchase, storage, and disposal of pressurized gas cylinders.

Scope

This guidance applies to laboratory spaces, chemical storage areas, and other workplaces owned or leased and maintained by UNR where pressurized gas cylinders are stored or used.

Responsible Authorities

  • Executive Vice President and Provost; Academic Departments
  • Vice President for Administration and Finance, Facilities Services Department
  • Vice President for Research and Innovation; Environmental Health and Safety Department

Background

Some pressurized gases have a limited safe storage lifetime due to potential for chemical reactions to occur inside of the storage cylinder which can result in over-pressurization of the cylinder or corrosion of the cylinder and/or cylinder valve. These conditions can lead to catastrophic failure of the cylinder or failure of the cylinder valve, resulting in uncontrolled release of the contents, which may be flammable, toxic, or reactive.

Pressurized gases can be purchased in cylinders that are owned by the gas supplier and rented by the gas purchaser, or in cylinders that are owned by the purchaser, either as previously owned cylinders or cylinders purchased with the pressurized gas. When pressurized gases are purchased in cylinders that are rented from the gas supplier the cylinder and any remaining pressurized gas can be returned to the supplier. This is the preferred situation since there is no cost to the purchaser for disposal of the cylinder and contents. Pressurized gas cylinders that are owned by the purchaser can be very expensive to dispose of, especially if the contents are considered to be a high reactivity hazard.

Proper safety practices require that pressurized gas cylinders be tracked and managed so that cylinders are not stored past their recommended safe storage lifetime. To avoid expensive disposal fees, pressurized gases should be purchased in cylinders that are owned by the gas supplier and rented by the user.

Definitions

Pressurized Gas: A gas which is contained in a receptacle at a pressure of 200 kPa (29 psi) (gauge) or more, or which is liquefied or liquefied and refrigerated. Pressurized gases include compressed gases, dissolved gases, liquefied gases, and refrigerated liquefied gases, as defined separately.

Compressed Gas: A gas which when under pressure is entirely gaseous at -50°C (-58°F), including all gases with a critical temperature 1 ≤ 50°C (-58°F).

Dissolved Gas: A gas which when under pressure is dissolved in a liquid phase solvent.

Liquefied Gas: A gas which when under pressure is partially liquid at temperatures above -50°C (-58°F). A distinction is made between:
(a) High pressure liquefied gas: a gas with a critical temperature 1 between -50°C (-58°F) and +65°C (149°F); and
(b) Low pressure liquefied gas: a gas with a critical temperature 1 above +65°C (149°F).

Refrigerated Liquefied Gas: A gas which is made partially liquid because of its low temperature.

Responsibilites

Deans, Department Chairs, and Directors

Ensure that all faculty, PIs, and workplace supervisors are aware of the responsibilities and procedures contained in this policy. Provide administrative support and enforcement of this policy in laboratories and other workplaces within their scope of responsibility.

Departments and Other Administrative Units

Ensure that pressurized gas cylinders that are used by, or stored in, laboratories and other work spaces which are assigned to the department or administrative unit are managed in accordance with this policy.

Assign a responsible person to manage pressurized gas cylinders in laboratories and other work places for which there is not a clearly recognized supervisor (for example, teaching laboratories or workplaces used by multiple groups).

Principal Investigators and Workplace Supervisors

Ensure that pressurized gas cylinders that are used by, or stored in, laboratories or other workplaces for which they are the responsible supervisor, and other pressurized gas cylinders for which they are responsible, are purchased, stored, and disposed of as specified by this policy.

Environmental Health & Safety (EH&S)

Provide specific guidance as requested by Principal Investigators (PIs) and other workplace supervisors with regard to safety issues associated with storage and disposal of pressurized gas cylinders. Coordinate disposal of university-owned pressurized gas cylinders.

Procedure

Purchase of Pressurized Gases

  1. Pressurized gases should be purchased in quantities that can be expected to be used within the safe storage lifetime recommended by the gas manufacturer or supplier.
  2. Whenever possible, purchase pressurized gases in cylinders that are owned by the gas supplier and which can be returned, along with any unused contents, to the supplier.
  3. If a pressurized gas can only be obtained by purchasing the associated gas cylinder, the purchaser is responsible for ensuring that the cylinder and any unused contents can be returned to the gas supplier for disposal at no additional charge, and obtaining a written agreement to this effect is strongly recommended.
  4. If gas cylinders that are owned by a university department or other administrative unit are refilled by a gas supplier, the purchaser of the gas is responsible for ensuring that any unused gas can be returned to the gas supplier for disposal at no additional charge, and obtaining a written agreement to this effect is strongly recommended.

Storage of Pressurized Gases

  1. Pressurized gas cylinders may not be stored or used for a period of time that exceeds the safe storage lifetime recommended by the pressurized gas manufacturer or supplier. The safe storage lifetime for a pressurized gas cylinder which is initially received at another institution or facility and later transferred to the UNR campus, begins on the date of initial receipt from the supplier.
  2. The storage lifetime for pressurized gas cylinders containing the following chemicals at a concentration of 50% or greater of the total cylinder contents is two calendar years from the time of initial receipt from the supplier.
    • Hydrogen fluoride
    • Hydrogen chloride
    • Hydrogen bromide
    • Hydrogen cyanide
    • Hydrogen sulfide
    • Nitric Oxide
    1. Any additional pressurized gases that are recognized as representing a similar level of reactive hazard during storage are also subject to a two year storage lifetime. Identification of additional pressurized gases that would be subject to the two year storage lifetime may be made based on published recommendations, a report of an environmental health and safety incident, or personal knowledge or experience.
    2. If the manufacturer or supplier specifically recommends a storage lifetime that exceeds two years, the longer lifetime may be used if there is a written agreement with the manufacturer or supplier to take back the cylinder, and any unused contents, up to the date of the stated storage lifetime.
  3. Each PI or workplace supervisor must ensure that the storage lifetime of each pressurized gas cylinder for which they are responsible is tracked, and that the storage lifetime does not exceed the guidance provided by the manufacturer or supplier, or the storage lifetime requirements listed in this policy.
    1. Cylinder inventory and safe storage lifetime must be tracked using the ChemTracker chemical inventory system that is used for other chemicals on campus. The PI or workplace supervisor is responsible for notifying Luis Barthel-Rosa in EH&S (luisbr@unr.edu) upon receipt of each pressurized gas that has an assigned safe storage lifetime so that information can be entered into the ChemTracker system.
  4. Pressurized gas cylinders for which a specific safe storage lifetime has not been established should be disposed of when no longer needed. This determination will normally be left to the PI or workplace supervisor but in instances where safe storage of a cylinder is in question, or it is clear that the cylinder is no longer being used, the EH&S Department can specify that the cylinder be disposed of.

Disposal of Pressurized Gases

  1. Unwanted pressurized gas cannot be deliberately vented from its cylinder for the purpose of disposing of the gas.
  2. Supplier-owned pressurized gas cylinders, and any unused contents, must be disposed of by returning cylinders to the vendor. The person who is responsible for the pressurized gas cylinder is responsible for contacting the vendor and coordinating its return to the vendor.
  3. Except when a gas supplier has agreed to take back a university-owned pressurized gas cylinder, and any unused contents, disposal of university-owned pressurized gas cylinders must be coordinated through the EH&S Department. Requests for disposal should be made using the online chemical waste disposal request form available on the EH&S web site ( unr.edu/ehs).
  4. The purchaser is responsible for the cost of disposal of pressurized gas cylinders that are owned by the university, and any unused contents of the cylinders. Failure of the purchaser to obtain a written agreement specifying that the cylinder, and any unused contents, may be returned to the supplier for disposal does not relieve the purchaser from this financial responsibility.
  5. In instances where the purchaser or other person responsible for a university-owned pressurized gas cylinder has left the university or cannot be identified, the responsible department, college, or other administrative unit will be responsible for the cost of disposal of the cylinder and any contents.

Related Material

Chemical Hygiene Plan