Purchase
Gases may be purchased in single-use cylinders or in reusable cylinders. Single-use cylinders have high initial purchase and disposal costs associated with them. Though reusable cylinders carry a rental fee (demurrage charge) while in possession of the customer, they are a more cost-effective and sustainable option.
USC Mailing and Material Management Services (MMMS) supplies returnable cylinders of a number of common gases and gas mixtures; see the list of gases available in stock. MMMS has limited oxidizers and flammable quantities on hand due to safety regulations, but can place special orders as needed.
Third-party gas suppliers can provide gases not carried by MMMS. Major third-party gas suppliers include Airgas, Gilmore Liquid Air Company, Linde (Praxair), and Matheson.
Inventory
Gases are chemicals and are subject to the same inventory requirements as all other hazardous materials. This includes all cylinders of compressed, liquefied, or refrigerated/cryogenic gases (including inert gases and lecture size bottles). Additionally, all non-pressurized cryogen dewars which are larger than hand-held need to be inventoried. NOTE: Many labs forget to include gas cylinders in their chemical inventory, a common inspection finding.
Ensure that gas cylinders are properly tracked via EHSA or Risk & Safety Solutions (RSS). Labs that were transitioned to RSS via the EH&S Chemical Inventory team have certified chemical inventories that include tagged gas cylinders.
Disposal
Prior to cylinder return and/or pick-up, ensure that the cylinder valve is closed and the regulator removed. Replace the protective cap (not available for lecture bottles). Mark or tag empty cylinders as EMPTY and store in a designated area separate from full or in-use cylinders to avoid confusion – dangerous back flow can occur when an empty cylinder is attached to a pressurized system. See Gas Storage and Transport for more information.
Gas cylinders purchased from third-party gas suppliers are expensive to dispose of, so every effort should be made to have the original manufacturer or supplier pick-up empty or unwanted cylinders. Per the Hazardous Waste Management Manual, obtain compressed gas cylinders from vendors who take back or exchange cylinders whenever possible. A few helpful tips:
- Negotiate with vendors to rent gas cylinders instead of purchasing.
- Ask vendors for a full list of gases that can be returned and refilled.
- Most vendors will not take back lecture bottles because they are not refillable.
Gas cylinders with unknown contents are even more expensive to dispose of. Labs are responsible for ensuring labels on all their hazardous materials are legible at all times. Replace damaged or unreadable labels. See the Compressed Gas Cylinder Disposal Fact Sheet for more information.
Questions? Email hazmat@usc.edu or call (323) 442-2200.