2.5% (50%LEL) CH4, 18%O2, 25ppm H2S, 100ppm CO, 34L | BW

This is a 34-litre (34 L) disposable (or non-refillable) calibration gas cylinder, containing a quad-gas mixture tailored for bump testing and calibration of four-gas portable gas detectors. The blend includes methane (CH?), oxygen (O?), hydrogen sulfide (H?S), and carbon monoxide (CO), with nitrogen (N?) as the balance gas.

• Methane (CH?) is present at 2.5% by volume, which corresponds to about 50% of the Lower Explosive Limit (LEL) for methane. This means the gas mixture can test the combustible or LEL sensor on a gas detector.
• Oxygen (O?) is at 18%, which is lower than ambient “normal air” (~20.9%) — this helps simulate oxygen-depleted environments while still being safe to handle.
• Hydrogen Sulfide (H?S) is at 25 ppm, a low but hazardous concentration often used in calibration, especially for detectors measuring very toxic gases.
• Carbon Monoxide (CO) is present at 100 ppm, enabling calibration of CO sensors as well.
• The rest of the gas volume is typically nitrogen (N?), which acts as a diluent / balance gas.

These cylinders are used to bump-test (perform a functional test) or span-calibrate multi-gas detectors. During a bump test, the detector’s sensors are exposed to this known concentration, and the instrument must respond within expected limits — verifying correct sensor operation. For calibration, the device is adjusted (if necessary) to read accurately for that gas mixture.

The 34 L size gives a good balance: enough gas for many calibration or bump-test cycles, while remaining compact and portable. These cylinders typically have a C-10 (5/8″-18 UNF) valve (or equivalent), compatible with standard demand-flow or fixed-flow regulators used in field calibration.

Because the gas mix includes flammable CH?, plus toxic CO and H?S, these cylinders are handled under hazardous-gas (HAZMAT) precautions, and come with a Certificate of Analysis (CoA) for quality assurance. The cylinders may also have a limited shelf life (often 12–24 months, depending on supplier) to ensure gas stability

Cylinder Material

Usually aluminium (for lightweight, portable use)

Valve Type / Connection

Commonly C-10 (5/8″-18 UNF)

Pressure

Depending on the manufacturer, but common for similar 34 L gas cylinders is ~500 psi / 35 bar for non-refillable

Shelf Life

Often 12–24 months, depending on the supplier and storage conditions. Example: Calgaz 34L 2.5% CH? / 25 ppm H?S cylinder has 24 months shelf life

Accuracy / Certification

Supplied with a Certificate of Analysis (CoA), often NIST- or ISO-traceable, depending on manufacturer. (For example, Calgaz version provides NIST-traceable CoA.)

Use Case / Application

- Bump-testing portable gas detectors (especially 4-gas detectors)
- Span-calibration of multi-gas sensors
- Verifying sensor response for LEL, O?, H?S, CO
- Safety / maintenance / calibration labs in industrial, petrochemical, confined-space environments

Safety Considerations

- Gas is flammable due to CH? component.
- Toxic components (CO, H?S) require proper ventilation, safety handling.
- Use with proper regulator and flow control device.
- Storage and transport may need to follow hazardous-gas cylinder norms.

Advantages & Benefits

• Multi-gas calibration: Because it has four gases (combustible, toxic, oxygen), it’s very efficient for calibrating 4-gas detectors in one go.
• Compact & portable: 34 L size provides a good number of tests while staying manageable to carry to field locations.
• Reliable response: The concentrations are chosen to give a meaningful test for both flammable and toxic sensors.
• Traceable quality: With a CoA, you can be confident in the accuracy of the gas mix for calibration/audit purposes.

Limitations / Drawbacks

• Limited life: Shelf life means you need to use or replace before expiration.
• Gas consumption: If performing many calibrations, the 34 L volume may run out; higher-volume cylinders may be needed.
• Safety risk: Toxic and flammable gases mean stricter handling procedures.
• Regulator compatibility: You need compatible regulators (demand-flow or fixed-flow) that can deliver the correct flow rate for your detectors.