While helping a commenter on Facebook’s Torch Talk Group find the correct fittings for connecting a Mad Hatter manifold to a flashback arrestor, I recognized that the cryptic names and numbers of torch connection fittings can be a bit daunting to the uninitiated.

If you are looking for the name of the fitting to connect manifolds, plumbing, flame arrestors and other fittings to weld hoses and torches – look no further:

CGA-022-B for Oxygen connections to torches

CGA-023-B for Fuel connections to torches

Understanding how CGA fittings are named isn’t just for engineers — it’s critical for anyone working with gas cylinders, regulators, or torches. The CGA system provides a standardized way to match fittings to their correct gas service, preventing dangerous cross-connections and costly downtime. In this guide, we’ll break down the CGA-023 B fitting as an example, explain what each part of the code means, and provide a practical chart of common CGA connections so you can make confident, safe selections for your equipment.

Understanding CGA Fitting Nomenclature — Breaking Down CGA-023 B

When working with gas cylinders, regulators, and hoses, every detail in a fitting’s label matters. Take CGA-023 B for example: here’s what each component tells you, and why it’s vital for safety and compatibility.

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1. CGA — the standard behind the name

“CGA” stands for Compressed Gas Association, a U.S. organization that defines standard connection patterns for cylinder gases so that equipment from different manufacturers can interface safely. These connection standards (often referenced in CGA’s V-1 standard) prevent mis-mating of dissimilar gases.

In other jurisdictions or industries, you might see alternative systems (e.g. DIN, ISO, or European cylinder standards), but in North American gas supply and welding/gas fitting practice, “CGA” is the dominant convention.

These standards map each gas (or gas family) to a specific connection code, so you can’t accidentally connect, say, an oxygen hose to a fuel cylinder with the wrong threading or shape.

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2. 023 — interpreting the numeric code

The number “023” designates a specific connection geometry under the CGA system. In the case of CGA-023, you are looking at the B-size, left-hand thread fuel gas fitting. More precisely:

• The “02x” family of CGA codes generally refers to B-size connections in the CGA V-1 list, suitable within a certain pressure and application envelope.
• The difference between 023 and 022 is critical:
   • CGA-022 is the right-hand, B-size fitting intended for oxygen service. Its threading is .5625-18 UNF, RH.
   • CGA-023, conversely, is left-hand, same B-size geometry, reserved for fuel/combustible gases, so that a fuel regulator can’t be (mistakenly) attached to an oxygen cylinder.
• More broadly, numbers in the CGA chart map to particular gases or gas classes (oxygen, inert, fuel, toxic, etc.) and thread styles. For instance, CGA-580 is common for inert gases like nitrogen or argon under high pressure.

So, seeing “023” immediately flags to a trained user that it’s a fuel-gas, left-hand B-size interface.

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3. B — the size class

The trailing letter (A, B, C, D, etc.) in a CGA designation refers to the size class of the fitting — essentially a shorthand grouping of thread diameter / flow capacity categories. In practice:

• B-size is one of the more common classes for welding or small industrial fuel and oxygen lines. Because it balances adequate flow and compact form, many regulators, hoses, and torches are built around B-size fits.
• There are C-size, D-size, and other variants in CGA’s universe (for higher flow or special uses), but in many small shop or torch setups they are less frequently encountered — so “B” is a practical default.
• Not every CGA code uses all size letters. Sometimes the size designation is implicit in the number (e.g. CGA-580 is by convention a B-size geometry in many implementations).
• When checking or ordering fittings, the letter helps ensure you’re matching the regulator, hose, or cylinder side correctly — mismatches in size class (even if the gas code portion is right) can lead to leaks, pressure drop, or rejection at inspection.

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Quick Reference: Common CGA Codes

CGA Code	Gas Type / Use	Thread Direction	Size	Typical Application
CGA-021	Fuel gas (acetylene, propane)	LH (left-hand)	B	Fuel gas cylinders and torches
CGA-022	Oxygen	RH (right-hand)	B	Oxygen regulators and torch equipment
CGA-023	Fuel gas (acetylene, LPG)	LH (left-hand)	B	Fuel regulator connection (B-size)
CGA-320	Carbon Dioxide (high pressure)	RH	Various	Beverage CO₂ systems
CGA-540	Oxygen (high pressure)	RH	—	Industrial oxygen cylinders
CGA-580	Inert gases (N₂, Ar, He)	RH	—	Shielding gases, nitrogen service
CGA-346	Compressed air	RH	—	Shop air, breathing air systems

Tip: Left-hand threads are typically identified by a notched hex nut or grooved fitting. If the fitting won’t start by hand, don’t force it — double-check the CGA code.

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Why These Codes Matter in Practice

Choosing fittings by CGA code isn’t just about matching threads — it’s about ensuring gas service compatibility, safety, and compliance. A CGA-023 B fitting is intentionally incompatible with CGA-022 to prevent a potentially dangerous oxygen-fuel mix-up.

When ordering, always confirm:

• CGA number (gas/service)
• Thread direction (LH vs RH)
• Size class (B, C, etc.)

This ensures that regulators, hoses, and cylinders work as a matched system, reducing the chance of leaks or catastrophic failure.

Still have questions? Our expert system designers are happy to guide you: