2.5% (50%LEL) CH4, 18%O2, 25ppm H2S, 100ppm CO, 58L | BW

The Gasco 58 L-421 calibration gas cylinder (sometimes referred to as “58L-421”) is a quad-gas mixture designed for bump testing, calibrating, and verifying multi-gas detectors. This particular blend includes:

• Methane (CH?) at 2.5% by volume, which represents 50% of its Lower Explosive Limit (LEL) — this allows for checking the combustible / LEL sensor response.
• Oxygen (O?) at 18% by volume — simulating reduced-oxygen environments.
• Hydrogen Sulfide (H?S) at 25 ppm, to test the toxic-gas sensor’s sensitivity.
• Carbon Monoxide (CO) at 100 ppm, for CO sensor verification.
• The balance of the gas is nitrogen (N?), which acts as an inert diluent.

The cylinder itself is made from aluminum, making it relatively lightweight yet rugged. The valve connection is C-10 (5/8″–18 UNF), a common standard for calibration gas regulators. 

This gas cylinder is typically used in industrial safety, maintenance, and calibration labs for periodic bump tests (functional checks) and span calibrations of portable gas detectors. By exposing a detector to this known mixture, you can verify whether the combustible (LEL), oxygen, H?S, and CO sensors are working correctly and within their expected response window.

Because of the presence of flammable gas (methane) and toxic gases (H?S and CO), this cylinder must be used with proper safety precautions — good ventilation, correct flow regulator, and certified calibration procedures are essential. The gas is supplied with a Certificate of Analysis (CoA) / calibration sheet to ensure traceability and accuracy, which is especially important for regulatory compliance and audit trails.

Gas Composition

2.5% CH? (50% LEL), 18.0% O?, 25 ppm H?S, 100 ppm CO, balance N?

Cylinder Volume

58 Litres

Cylinder Material

Aluminum alloy

Service Pressure

~500 psi for 58 L aluminum cylinder.

Certifications / Traceability

Calibration certificate / CoA; NIST-traceable (depending on supplier)

Use Cases

- Calibration of multi-gas detectors (LEL, O?, H?S, CO)
- Bump tests / functional checks
- Safety maintenance / compliance labs
- Confined-space and industrial gas-detection calibration

Safety Considerations

- Flammable (methane)
- Toxic (CO, H?S)
- Use correct regulator + tubing
- Follow gas cylinder and HAZMAT handling practices
- Use in well-ventilated area or under controlled gas flow conditions

Advantages / Benefits

• Comprehensive calibration mix: Four critical gases in one cylinder means you don’t need separate cylinders for each sensor.
• Longer usage: With 58 L volume, you can perform more calibration / bump cycles compared to smaller cylinders, making it cost-efficient for frequent use.
• Portability: Aluminum build keeps weight low for easier handling.
• Traceability: Comes with a calibration certificate, ensuring that your gas detectors are calibrated against a reliable standard.
• Regulated safety: Using a known gas mix helps ensure detectors respond correctly, which is critical for worker safety and compliance.

Limitations / Considerations

• Gas consumption: Although 58 L is substantial, repeated calibration may exhaust the cylinder, so plan your gas orders.
• Shelf life / stability: Calibration gases can degrade over time; check the CoA and expiration / recommended use period.
• Regulator requirement: You must use a compatible demand-flow or fixed-flow regulator (C-10 compatible) to ensure safe and correct gas delivery.
• Hazard risk: Due to flammable and toxic components, you need to strictly follow safety and handling procedures.