4-Gas Calibration Cylinder — Complete Guide for CO, H₂S, O₂, and LEL Bump Testing
The 4-gas calibration cylinder — commonly called a quad gas cylinder — is the most widely used calibration gas in portable gas detection. It contains four gases at once: Carbon Monoxide (CO), Hydrogen Sulfide (H₂S), Oxygen (O₂), and a combustible gas for Lower Explosive Limit (LEL) calibration. The gas we supply is produced in ISO/IEC 17025:2017-accredited laboratories, ships with a NIST-traceable Certificate of Analysis, and is available in all standard sizes for same-day shipping.
What is a 4-gas calibration cylinder?
| Gas | Symbol | Standard concentration | Hazard |
|---|---|---|---|
| Carbon Monoxide | CO | 100 ppm | Toxic |
| Hydrogen Sulfide | H₂S | 25 ppm | Toxic |
| Oxygen | O₂ | 18% (deficiency) | Oxygen |
| Methane (LEL) | CH₄ | 50% LEL (2.5% CH₄) | Combustible |
The most common 4-gas mixture — the “380 mixture” — contains exactly these four gases at these concentrations and is the universal standard for most portable 4-gas detectors.
Bump test vs. full calibration
Bump test (function check): exposes the detector to gas to confirm each sensor responds and alarms — it does not adjust the detector. Recommended before each use, or at least daily for IDLH environments.
Full calibration (span): adjusts the sensor readings to match the known concentration, correcting drift. Typically every 30–180 days depending on use and sensor type.
Which cylinder size do I need?
| Cylinder | Approx. bump tests | Approx. calibrations | Best for |
|---|---|---|---|
| 17L-380 | ~100 | ~30 | 1–2 detectors, field use |
| 34L-380 | ~200 | ~60 | Standard — most common |
| 58L-380 | ~350 | ~100 | Multiple detectors |
| 103L-380 | ~600 | ~180 | Safety teams, 5+ detectors |
Common 4-gas mixtures — part numbers
| Part # | CO | H₂S | LEL / CH₄ | O₂ | Common detector |
|---|---|---|---|---|---|
| 34L-380 | 100ppm | 25ppm | 50% LEL | 18% | MSA, BW, iSC |
| 34L-383 | 100ppm | 25ppm | 2.5% CH₄ | 18% | Multiple brands |
| 34L-421 | 100ppm | 25ppm | 1.45% CH₄ | 15% | MSA Altair 4X |
| 34L-486 | 50ppm | 10ppm | 50% LEL | 18% | Low-range detectors |
| 34L-491 | 50ppm | 25ppm | 0.7% Pentane | 18% | Pentane LEL sensor |
| 58L-421 | 100ppm | 25ppm | 1.45% CH₄ | 15% | MSA Altair 4X fleet |
Which mixture for my detector?
| Detector | Recommended mixture | Part # |
|---|---|---|
| MSA Altair 4X | 25ppm H₂S / 100ppm CO / 1.45% CH₄ / 15% O₂ | 34L-421 or 58L-421 |
| MSA Altair 5X | 25ppm H₂S / 100ppm CO / 50% LEL / 18% O₂ | 34L-380 or 58L-380 |
| BW GasAlert Quattro | 25ppm H₂S / 100ppm CO / 50% LEL / 18% O₂ | 34L-380 |
| BW Micro Clip XL | 25ppm H₂S / 100ppm CO / 50% LEL / 18% O₂ | 17L-380 or 34L-380 |
| Industrial Scientific MX6 | 25ppm H₂S / 100ppm CO / 50% LEL / 18% O₂ | 34L-380 or 103L-380 |
| Draeger X-am 5000 | 25ppm H₂S / 100ppm CO / 50% LEL / 18% O₂ | 34L-380 |
Always verify the required concentration in your detector’s user manual — manufacturer specifications take precedence. Need help confirming? Email sales@trigas-usa.com.
Auto-Replenish for 4-gas cylinders
A 4-gas cylinder is a consumable. With Auto-Replenish you choose your mixture, size, and a 30/60/90-day interval for 8% off plus free shipping, with a reminder before each delivery and CoA/SDS included. Modify, pause, or cancel anytime; Net-30 available for B2B.
FAQ
What does 50% LEL mean? Half the Lower Explosive Limit. For methane (LEL 5% by volume), 50% LEL = 2.5% CH₄ — safe to ship while still triggering the combustible sensor.
Can I use any 4-gas cylinder with my detector? The mixture must match your sensor configuration and concentration range. Most use the 380 mixture; some (e.g. MSA Altair 4X) need 15% O₂. Check your manual.
How long does a 34L-380 last? Roughly 150–200 bump tests, depending on regulator flow, test duration, and temperature.
Questions? Call (786) 609-3221 or email sales@trigas-usa.com.