Compressed Gas Cylinders


Compressed Gas CylindersCompressed gas cylinder management is an ongoing concern for public agencies, hazardous waste generators (Including households), hazardous waste transporters, and Transportation, Storage, and Disposal Facilities (TSDFs). Ongoing issues with discovery of cylinders in household hazardous waste, household garbage, sites with large accumulations of cylinders of varying types with no labeling, damaged labeling, or incorrect labeling creates problems for companies and agencies to properly manage compressed gas cylinders.

This guidance is to assist businesses on proper management of compressed gas cylinders. Compressed gas cylinders must be properly managed, even before they are wastes. However, DTSC does not manage compressed gases when they are still product. When the cylinders or the contents within them become wastes, then they come under potential regulation as hazardous waste, depending on the characteristics of the gases that are contained within them. Contained within this guidance are references from U.S. EPA that may assist in management of compressed gas cylinders.


Frequently Asked Questions

I have compressed gas cylinders that are returned and refilled. Are these cylinders wastes?

U.S. Environmental Protection Agency (EPA) determined that compressed gas cylinders that are returned by customers for re-use, refilling, and re-issue are not considered wastes. The decision on when a cylinder or the contents of the cylinder are a waste is made by the owner of the cylinder. Once a decision has been made to discard any remaining contents of the cylinder, and/or the cylinder itself, then it may need to be managed as a hazardous waste. Hazardous waste characterization is needed to determine if the compressed gas cylinder needs to be managed as a hazardous waste.

Description: Residual gases in a cylinder transported with minimum pressure as a matter of safety are not regulated as hazardous waste because it has not been discarded. The material is not discarded until the cylinder reaches the supplier and a decision is made whether to discard the residual gas. Returning the cylinder to the supplier does not make the customer a hazardous waste generator.


Are discarded compressed gas cylinders waste?

Title 22 of the California Code of Regulations (22 CCR) defines waste and hazardous waste. If an item meets the definition in 22 CCR 66261.2, then it is a waste.

The gases need to be characterized to know if they are a hazardous waste. A hazardous waste is defined in 22 CCR 66261.3, and includes acutely hazardous waste, extremely hazardous waste, non-RCRA hazardous waste, RCRA hazardous waste, special waste and universal waste.

NOTE: DTSC does not agree with the US EPA decision. Please see the following letter:

EPA letters:

Description: Discarded compressed gas cylinders containing gaseous, liquid, or physically solid (i.e., non-empty containers) the residues in the cylinders become hazardous wastes because they are being discarded and the residues and cylinders must be handled in compliance with the RCRA regulations. Wastes removed from or derived from the treatment of the cylinders may also be regulated as hazardous waste. Any gas cylinder handling facility is not subject to RCRA regulations in the handling, neutralization, scrubbing, flaring, or venting of gaseous residues removed from compressed gas cylinders.

Description: Liquid or physical solid wastes removed from compressed gas cylinders are solid wastes. Gaseous residues are not solid wastes.

Description: 261.21(a)(3) should refer to a flammable compressed gas, not an ignitable compressed gas.


When is a compressed gas cylinder empty?

Under federal RCRA regulations, "A container that has held a hazardous waste that is a compresses gas is empty when the pressure in the container approaches atmospheric." 40 CFR 261.7 (b)(2).

22CCR 66261.7(l) states, "A compressed gas cylinder is exempt from regulation under this division and Chapter 6.5 of Division 20 of the Health and Safety Code when the pressure in the container approaches atmospheric pressure."

It is the position of DTSC that if a compressed gas cylinder valve is closed and has residual pressure, it is not considered empty. Thus, if a cylinder valve is left open, it is an "empty cylinder."

Description: Provides a summary of the empty container regulations. If the waste is a compressed gas, then the container is empty when the pressure in the container approaches atmospheric pressure.

How do I manage hazardous waste gases?

Remaining gases in the cylinders will need to be appropriately managed of them via appropriate methods. Proper characterization of the hazardous waste gas is needed in order to determine the best management of the gas itself. Once it is determined what the characteristics of the gas are, then management may include reclamation, reuse, neutralization, venting, flaring, or other treatment. However, treatment of hazardous waste is generally only allowed at permitted Treatment, Storage, or Disposal Facilities (TSDFs), and is not generally allowed at the point of generation.


How do I manage the compressed gas cylinders?

Once a cylinder is empty and is to be discarded, it should be recycled. Scrap metal recycling companies sometimes have restrictions on the types of cylinders that they will take, or require that they be cut in half or for the cylinder valve be removed to prove that they are empty. Others will require that it be punctured prior to acceptance. As stated previously, if you are returning your cylinders to a location for refilling, they are not considered hazardous waste. Contact the receiving facility to determine their requirements prior to shipping compressed gas cylinders for reuse, recycling, or disposal.

Households should take their used cylinders to Household Hazardous Waste collection facilities. Compressed gas cylinders that are not empty are not to be disposed of in the trash. Contact the household hazardous waste facility, recycling or disposal facility to determine the requirements for their criteria to accept the cylinders.


Do I count compressed gas cylinders?

Yes. Hazardous waste cylinders must be counted when determining status as a small quantity or large quantity generator. However, empty compressed gas cylinders that are managed pursuant to 22CCR 66261.7(l) are not counted.


How do I identify the gas in a cylinder I have?

NOTE: Sampling and definitive laboratory analysis of the gas is the only method that will provide confirmation of an unknown. The following information is not to be taken as a definitive method to determine the gas you have.

Some simple methods exist to assist in the presumptive determination of the contents of a cylinder. (Go through cylinder identification here – shoulder labels, valves). The Compressed Gas Association (CGA) standard can assist in identification of the gas that may be in an unknown cylinder. Cylinder valves marked with "CGA" plus a 3 digit number correspond with a type of gas or gases that may be in the cylinder:

CGA Marking

Figure 1: Cylinder valve example

In this example, above the date code is CGA580. This valve code would indicate that the suspected gas in the cylinder would be Nitrogen, with less than 3,000 PSI. This, along with other information, including shoulder labeling, provides information that can assist with identification of unknown cylinders. Many gas suppliers have a list of the CGA codes on the valves. The CGA also makes the list available to members for free, and charge a fee to non-members.


Figure 2 - Example shoulder label


Where can I learn about Hazardous Waste Classification?

DTSC has a self-paced training program that anyone can take, free of charge. It includes the criteria for identification of hazardous waste.

Please go to DTSC's California Hazardous Waste Classification onine course to take this training.


Who can I contact with a question?

Your Certified Unified Program Agency (CUPA) can help you with questions regarding proper management of compressed gas cylinders. To determine your CUPA, please go to California Environmental Reporting System (CERS) and enter your city or county.

If you have further questions, the DTSC Regulatory Assistance Office can help you as well.

Contact the Regulatory Assistance Office

Where can I find letters from DTSC regarding compressed gases?

DTSC has a database of historical letters regarding many topics, including compressed gases, aerosol cans, cylinders, and more. Go to our DTSC Online Reference Library to access the letters.

For reference, some of these letters are provided below: