MIG mild steel
Most common short-circuit mild steel shielding setup.
C25CGA-580
Gas support
Welding Gas Reference Guide
CGA Numbers, Uses & Compatibility
Welding gases are not interchangeable. The wrong gas or wrong regulator connection can damage equipment, cause poor weld quality, or create a safety hazard. CGA numbers identify standardized cylinder valve and regulator connections so the correct regulator is matched to the correct gas.
What Are CGA Numbers?
CGA numbers are standardized connection specifications for compressed gas cylinder valves and regulator inlets. They exist to reduce the chance that the wrong regulator is connected to the wrong gas. Treat the CGA number as a safety check, not just a shopping detail.
Verify Before Ordering Confirm the CGA number on your cylinder, the regulator inlet connection, gas service, pressure rating, and supplier requirements before buying accessories.
Gas Quick Reference
| Gas | Primary Use | CGA # | Best Process | Guide |
|---|---|---|---|---|
| Argon | TIG shielding, MIG aluminum | CGA-580 | TIG / MIG aluminum | View guide |
| CO2 / Carbon Dioxide | MIG shielding, 100% or blended | CGA-320 | MIG | View guide |
| C25 / 75% Argon 25% CO2 | MIG mild steel | CGA-580 | MIG | View guide |
| Oxygen | Oxy-fuel cutting and welding | CGA-540 | Oxy-fuel | View guide |
| Acetylene | Oxy-fuel cutting and welding | CGA-510 | Oxy-fuel | View guide |
| Nitrogen | Purging, back-purging stainless | CGA-580 | TIG back-purge / pipe | View guide |
| Helium | TIG blends for deeper penetration | CGA-580 | TIG thick aluminum/copper | View guide |
| Tri-Mix / He-Ar-CO2 | Stainless MIG shielding | CGA-580 | MIG stainless | View guide |
CGA numbers are standardized by the Compressed Gas Association. Always verify with your cylinder supplier before ordering a regulator.
Most Common Welding Gas Setups
MIG stainless
Stainless MIG setups often use helium/argon/CO2 mixes.
Tri-MixCGA-580
MIG aluminum
Common shielding gas for aluminum MIG and spool gun work.
100% ArgonCGA-580
TIG all metals
Baseline TIG shielding gas for steel, stainless, aluminum, and many alloys.
100% ArgonCGA-580
TIG thick aluminum/copper
Helium blends can add heat input and penetration.
Argon/Helium blendCGA-580
Oxy-fuel oxygen
Oxygen regulator connection for cutting and welding setups.
OxygenCGA-540
Oxy-fuel acetylene
Acetylene regulator connection for standard acetylene cylinders.
AcetyleneCGA-510
Back-purge stainless pipe
Common purge/back-purge gas path when procedure allows.
NitrogenCGA-580
Heavy structural MIG
Used in some heavy MIG setups; requires CO2 regulator connection.
100% CO2CGA-320
Buy the Right Cylinder Size
Use the same general cylinder size thinking for argon, C25, helium blends, and nitrogen: match run time, portability, local refill policy, and storage safety. Do not assume filled cylinders can be shipped or purchased online.
20 cu ft
Typical use: Small home or repair jobs
Portability: Most portable; useful for light TIG/MIG practice or occasional use.
Use case: Short sessions and backup cylinder
Amazon link: needs verification40 cu ft
Typical use: Light shop use
Portability: Still portable while giving more run time than a 20 cu ft cylinder.
Use case: Small garage welding setups
Amazon link: needs verification80 cu ft
Typical use: General garage/shop use
Portability: Common balance between portability and run time.
Use case: MIG/TIG hobby and repair work
Amazon link: needs verification125 cu ft
Typical use: Frequent shop use
Portability: Less portable, better for recurring welding projects.
Use case: Regular MIG/TIG welding
Amazon link: needs verification250 cu ft
Typical use: Production or high-use shop
Portability: Large cylinder, usually cart- or wall-secured.
Use case: Frequent welding or purge-gas use
Amazon link: needs verificationHigh-Pressure Gas Safety
Compressed gas cylinders are high-pressure vessels. Secure cylinders upright, use the correct regulator for the gas type, inspect connections before opening valves, and follow supplier and manufacturer guidance.
- Never use oil or grease on oxygen equipment.
- Do not adapt fittings to force a mismatched regulator onto a cylinder.
- Open cylinder valves slowly and stand to the side of the regulator.
- Use approved leak detector solution after setup.
Where to Buy Regulators and Accessories
As an Amazon Associate, Weld Support Parts may earn from qualifying purchases.
Unverified Amazon items are not shown as products or buy buttons. These cards show where future verified links can be added after CGA connection, gas service, regulator rating, package contents, and listing accuracy are checked.
Argon / C25 regulator
Use CGA-580 equipment for argon, C25, nitrogen, helium, and many tri-mix cylinders.
Amazon link: needs verificationCO2 regulator
Use CGA-320 equipment for carbon dioxide cylinders.
Amazon link: needs verificationOxygen regulator
Use CGA-540 oxygen-rated equipment and keep oil/grease away from oxygen service.
Amazon link: needs verificationAcetylene regulator
Use CGA-510 acetylene equipment and follow acetylene withdrawal and cylinder handling limits.
Amazon link: needs verificationFlowmeter
Use flowmeters rated for the gas and flow range required by the process.
Amazon link: needs verificationGas hose
Match hose type, fittings, gas service, and pressure rating before use.
Amazon link: needs verificationFlashback arrestor
Use oxy-fuel flashback arrestors and check valves where appropriate.
Amazon link: needs verificationCylinder cart
Secure cylinders upright and choose a cart rated for the cylinder size.
Amazon link: needs verificationFAQ
Can I use the same regulator for every welding gas?
No. Regulator inlet connections, materials, pressure ratings, and gas service must match the cylinder and gas. Always verify the CGA number and regulator rating before connecting.
Can I buy filled welding cylinders online?
Do not assume filled gas cylinders are available online. Many filled cylinders require local supplier exchange, lease, or refill policies. Online buying is more appropriate for verified empty cylinders and accessories.
What CGA connection is used for argon and C25?
Argon, C25, nitrogen, helium, and many tri-mix cylinders commonly use CGA-580 connections, but users should still verify with the cylinder supplier.
What is the safest way to size a cylinder?
Choose a cylinder size based on process, expected run time, portability, refill access, and how securely the cylinder can be stored upright.