CGA’s S-1 Series: What Distributors Need to Know About Pressure Relief Device Standards

* Originally published by CGA in GAWDA Magazine.

In the world of compressed gases, safety is not optional—it’s essential. One of the most critical components in ensuring the safe use, storage, and transportation of compressed gas and cryogenic fluid containers is the pressure relief device (PRD). These devices are designed to protect containers from rupture due to excessive pressure, helping prevent catastrophic incidents in facilities, on delivery trucks, and in customer operations.

The Compressed Gas Association (CGA) maintains a robust suite of standards governing pressure relief devices. Chief among them is the S-1 series, comprised of:

  • CGA S-1.1, Pressure Relief Device Standards—Part 1: Cylinders for Compressed Gases
  • CGA S-1.2, Pressure Relief Device Standards—Part 2: Cargo and Portable Tanks for Compressed Gases
  • CGA S-1.3, Pressure Relief Device Standards—Part 3: Stationary Storage Containers for Compressed Gases

These three publications are the most comprehensive industry standards available on PRDs and are designed to serve everyone from container manufacturers and requalifiers to gas distributors and end users. Understanding and applying the guidance in these documents can significantly reduce risk in your operations and improve overall safety performance.

S-1.1: Cylinders for Compressed Gases

CGA S-1.1, which had its 17th edition published on 3/19/2025, covers PRDs used on refillable and nonrefillable compressed gas cylinders, including industrial, medical, and specialty gases. This standard details the design, manufacture, selection, installation, and testing of pressure relief devices, including:

  • Fusible plugs
  • Rupture discs
  • Combination devices
  • Pressure relief valves

CGA S-1.1 provides specific guidance on how to determine appropriate PRDs for different gas services and cylinder sizes. It also outlines performance requirements and acceptance criteria for PRDs, helping ensure consistency across suppliers and operations.

CGA S-1.1 is an essential reference for anyone involved in the filling, transportation, or inspection of compressed gas cylinders. Its latest edition reflects current best practices and aligns with regulatory requirements in the United States and Canada.

S-1.2: Cargo and Portable Tanks

CGA S-1.2, which had its 11th edition published on 9/24/2024, extends the PRD guidance to cargo and portable tanks—specifically, the larger mobile containers used to transport bulk quantities of compressed gases.

This standard is especially relevant to bulk gas distributors, offering a comprehensive review of PRDs for high-volume transportation. Topics include:

  • Relief valve sizing and flow capacity
  • Pressure settings and tolerances
  • Inspection, maintenance, and requalification intervals
  • Proper application of rupture discs and relief valves

Because portable tanks travel long distances and face varied environmental conditions, CGA S-1.2 emphasizes the importance of robust, redundant safety mechanisms and clear labeling requirements.

S-1.3: Stationary Storage Containers

The third part of the series, CGA S-1.3, which had its 11th edition publish 9/24/2024, addresses stationary storage containers—permanently installed vessels used in manufacturing plants, distribution hubs, and customer facilities.

This standard provides detailed requirements for:

  • PRD sizing and venting for both horizontal and vertical vessels
  • Installation configurations to prevent obstruction or tampering
  • Requirements for relief valve set pressures, reseating capabilities, and testing
  • Considerations for environmental exposure and product-specific hazards

CGA S-1.3 is vital for ensuring long-term storage safety, particularly in high-use customer sites or distributor-owned bulk installations.

Why These Standards Matter

Our members play a frontline role in compressed gas safety. From cylinder delivery routes to on-site storage systems, distributors are responsible for ensuring that equipment is properly configured, that PRDs meet code, and that systems are safe and compliant.

The S-1 series provides trusted, up-to-date technical information directly from the industry’s most experienced experts. These standards are referenced by groups like the National Fire Protection Association (NFPA) and International Codes Council (ICC).

Following these standards can help your team:

  • Avoid improper PRD installations that may lead to leaks or rupture
  • Ensure pressure relief devices are suitable for the specific gas and cylinder
  • Comply with DOT, OSHA, NFPA, and Transport Canada regulations
  • Minimize liability and protect personnel, property, and customers

Access the Standards—and So Much More—Join CGA

If your company is not a CGA member, now is the time to join. This exclusive benefit gives everyone at your company free digital access to the entire CGA library, including the S-1 series and more than 385 other safety publications.

Here’s what’s included at no cost:

  • ✅ Full access to CGA’s complete electronic library of nearly 400 compressed gas safety standards
  • ✅ Self-paced eLearning modules for training employees anywhere, anytime
  • ✅ Customizable safety posters for cylinder handling, storage, and end-user education
  • ✅ Virtual access to the CGA Handbook of Compressed Gases, covering 58 gases with detailed safety information
  • ✅ Discounted access to CGA events like the Technical Summit, YEP Summit, and webinars.
  • ✅ Member pricing on hard copy orders of any CGA publication

For questions about the S-1 series or how to get the most value out of your CGA resources, please feel free to reach out to us at cga@cganet.com.

About the Compressed Gas Association

Founded in 1913, the Compressed Gas Association (CGA) is a global leader in the development of safety standards for the production, storage, transportation, and use of industrial, medical, food, and specialty gases. CGA has developed nearly 400 safety standards and is recognized by international bodies such as ISO, NFPA, and the United Nations. The association supports more than 34,000 U.S. jobs and contributes over $10 billion to the American economy, with each industry job supporting more than five additional jobs in related sectors. CGA remains committed to promoting safety, innovation, and professional development in the compressed gas industry.