What Is Flammable Gas (EX/LEL)? The Mechanics of Industrial Explosions
Flammable gas refers to any gas that, within a specific concentration range in air, can ignite explosively when a source of ignition is present—such as a spark, static electricity, or a hot surface. In industrial settings, the danger zone is defined by the LEL (Lower Explosive Limit) and UEL (Upper Explosive Limit). When concentrations reach 10% LEL, immediate evacuation is required.
💡 Key Point
Many flammable gases—methane (CH₄), hydrogen (H₂), LPG, ethanol vapor—are colorless and odorless, making human detection impossible. They can appear in chemical plants, power stations, wastewater facilities, and fuel stations alike.
Health and Safety Impact of Flammable Gas Exposure
| Concentration (LEL%) | Risk Level | Effects | Action |
|---|---|---|---|
| 0–10% | Caution | Low direct hazard; leak in progress | Ventilate; inspect source |
| 10–25% | Alarm | Fire risk if ignition source present | Stop work; begin evacuation |
| 25–100% | Danger | Explosion imminent; severe injury risk | Evacuate immediately; call emergency |
| >100% LEL | Extreme | Autoignition possible; fatal | Full evacuation; fire department |
※ CH₄: LEL 5%, UEL 15% / H₂: LEL 4%, UEL 75% (Source: KOSHA, IEC 60079)
Real Incident: Flammable Gas Explosion Casualties
Case 1 — 2019 Gangneung Hydrogen Tank Explosion (South Korea)
In May 2019, a hydrogen storage tank explosion at a research facility in Gangneung killed 2 and injured 6. Hydrogen's extremely low LEL of 4% means even a small leak is dangerous, yet no real-time hydrogen gas detector was present at the facility at the time. (Source: Korea National Fire Agency Accident Report, 2019)
WANDI EDW500 — IECEx Internationally Certified 5-Gas Detector
What Is IECEx Certification?
IECEx is the global certification scheme managed by the International Electrotechnical Commission (IEC) for electrical equipment in explosive atmospheres. The EDW500 holds:
- Certificate: IECEx TPS 25.0057X (certified by TÜV SÜD)
- Marking: Ex da ia IIC T4 Ga — suitable for Zone 0 (EPL Ga)
- Gas Group IIC: covers hydrogen and the most hazardous gas classes
- Temperature Class T4: max surface temperature ≤135°C
5-Gas Simultaneous Measurement
A single EDW500 measures EX (LEL), O₂, CO, H₂S, and CO₂ simultaneously. At sites where flammable gas leaks occur, oxygen deficiency and CO generation often accompany—making 5-gas monitoring a comprehensive safety solution far superior to standalone LEL detectors.
Accident Prevention Scenario with the EDW500
- 1Early Detection: Alarm triggers at 10% LEL — workers are immediately alerted
- 2Cloud Transmission: Live data sent via LTE/WiFi to supervisory monitoring system
- 3Second Alarm at 25% LEL: Evacuation order issued; ignition sources isolated
- 4Data Logging: Full measurement history stored in cloud for root-cause analysis and legal documentation
EDW500 Specifications — Flammable Gas Performance
| Item | Specification |
|---|---|
| Gases Measured | EX (LEL), O₂, CO, H₂S, CO₂ — 5 simultaneously |
| EX Range | 0–100% LEL |
| EX Alarm Thresholds | 1st: 10% LEL / 2nd: 25% LEL (adjustable) |
| Sensor Type | Catalytic bead or IR |
| Explosion Protection | IECEx TPS 25.0057X (TÜV SÜD), Zone 0 rated |
| Connectivity | LTE/WiFi real-time cloud upload |
| Battery Life | 8+ hours continuous operation |