Short answer: A calibration gas mixture is a precisely proportioned blend of two or more gases used to calibrate analyzers, validate methods and ensure quality control. Mixtures are built on a three-level hierarchy — primary, analytical and working standards — and prepared gravimetrically or by partial pressure. A full-service manufacturer offers 130+ standard mixture varieties, from gas-alarm blends (0.18%–3.0% LEL ranges) to 1ppm–100% petrochemical standards.
What is a calibration gas mixture?
Standard gas mixtures have uniform composition, accurate values and excellent stability. They are the reference materials that keep gas detectors, process analyzers, emission monitors and lab instruments honest. Without a certified mixture, a measurement is just a number.
The three-level standard gas hierarchy
| Level | Role |
|---|---|
| Primary standard (基准标准气) | The highest level; used to verify and calibrate lower-level standards |
| Analytical standard (分析用标准气) | Instrument calibration, method evaluation, quality assurance |
| Working standard (工作标准气) | Routine daily calibration of analytical instruments |
How standard gas mixtures are prepared
Two methods dominate:
- Gravimetric (mass-based) — components are weighed on high-precision balances; the reference method per ISO 6142.
- Partial-pressure — components are added by pressure; faster for routine blends but less accurate for trace levels.
A credible supplier states the preparation method and the guaranteed tolerance for each component.
Standard mixtures by application
1. Gas alarm mixtures (10%LEL – 60%LEL)
Used to bump-test and calibrate combustible and toxic gas detectors. Packaging is typically 1–8L cylinders.
| Component | Concentration range | Balance |
|---|---|---|
| CH₄ | 0.5 – 3.0% | Air |
| C₃H₈ | 0.22 – 1.32% | Air |
| C₄H₁₀ | 0.27 – 1.62% | Air |
| i-C₄H₁₀ | 0.18 – 1.08% | Air |
| H₂ | 0.40 – 2.40% | Air |
| CO | 100 – 500 ppm | Air |
| H₂S | 10 – 1000 ppm | N₂ |
2. Power & energy standards
Multi-component blends (CO, H₂, CO₂, CH₄, C₂H₆, C₂H₄, C₂H₂, O₂, N₂) with N₂ or Ar balance, matched to regional specifications (Shanghai/Jiangsu, Zhejiang, Fujian, Jiangxi, Shenzhen) for power-equipment online monitoring and environmental acceptance.
3. Petrochemical standards (1 ppm – 100%)
Hydrocarbon and inorganic reference gases: CH₄, C₂H₆, C₃H₈, n/i-butane, isopentane, n-hexane, ethylene oxide, methyl chloride, H₂S, SO₂, NH₃, and more — the backbone of refinery and plant analyzers.
4. Environmental monitoring standards (1 – 50000 μmol/mol)
Methane, propane, CO, CO₂, H₂, O₂ in air or nitrogen; NO, NO₂, SO₂, H₂S in nitrogen; vehicle-exhaust standards (CO 1–10%, CO₂ 1–15%); and C1–C6 hydrocarbon mixtures plus liquid standards.
How to specify a custom gas mixture
- Component + target concentration (with tolerance)
- Balance gas (Air, N₂, Ar, He)
- Cylinder size and pressure (e.g. 47L @ 10–13.8MPa)
- Valve type (DISS/CGA as required)
- Reference standard level (analytical vs working)
- Certification requirements (CoA, NIST-traceable values where applicable)
FAQ
Q1: What does “10%LEL–60%LEL” mean in an alarm gas?
LEL = Lower Explosive Limit. The mixture concentration is expressed as a percentage of the LEL (e.g. 10–60% of LEL), which is how gas detectors are typically calibrated for combustible gas.
Q2: How accurate are calibration gas mixtures?
Accuracy depends on the preparation method and level. Gravimetric primary standards achieve the tightest tolerances (often ±1–2% relative); working standards are slightly looser but sufficient for routine calibration.
Q3: What is the shelf life of a calibration gas?
Typically 12–24 months depending on the components and cylinder treatment; reactive gases (H₂S, NO, SO₂) have shorter stability. Check the CoA for the certified expiry.
Q4: Can you make a mixture with 100 ppm of a reactive gas like H₂S?
Yes — but reactive gases require cylinder passivation and careful handling to maintain stability. Choose a supplier experienced with passivated cylinders.
Q5: Do I need a custom mixture or an off-the-shelf one?
If your target matches a standard blend (e.g. a common alarm gas), buy off-the-shelf. Custom mixtures make sense for unusual components, concentrations or regional specs (like power-grid standards).
Q6: What documentation should come with a mixture?
A certificate of analysis listing each component, certified concentration, tolerance, balance gas, preparation method, cylinder ID and expiry date.
Q7: What is the difference between a standard gas and a specialty mixture?
Standard gases are certified reference materials for calibration. Specialty mixtures are process gases blended for an application (e.g. laser gas, doping gas). Newradar supplies both, from 130+ standard varieties to ppm-level specialty mixtures.
Sources
- ISO 6142 — Gas analysis: preparation of calibration gas mixtures (gravimetric method)
- ISO 6143 — Gas analysis: comparison methods for determining composition
- NIST standard reference materials program (gas mixtures)
- China national standards for gas detection and environmental monitoring calibration
- Newradar 2026 corporate brochure — standard gas mixtures section (www.nrdgas.com)
Post time: Aug-28-2026