What Is Methane (CH4)? The Invisible Explosion Hazard
Methane (CH4) is the primary component of natural gas and is naturally generated in sewage treatment plants, biogas facilities, landfills, coal mines, and livestock manure processing sites. It is colorless, odorless, and tasteless — completely undetectable by human senses — and when its concentration in air reaches 5–15% (100% LEL), a single ignition source is enough to trigger an explosion.
💡 Key Point
Methane is lighter than air and accumulates near ceilings and upper spaces. Upper zones must always be measured in enclosed spaces. Oxygen depletion often accompanies CH4 accumulation, making multi-gas detection essential.
CH4 Health Effects and Explosion Risk by Concentration
| Concentration | Hazard Type | Effect | Risk Level |
|---|---|---|---|
| 1,000 ppm (0.1%) | Explosion risk begins | LEL 10% — alarm threshold | 🟡 Caution |
| 5,000 ppm (0.5%) | LEL 50% | Immediate evacuation required; ignition risk | 🔴 Dangerous |
| 50,000 ppm (5%) | LEL 100% — lower explosive limit | Explosion occurs upon ignition | ☠️ Explosion Risk |
| 150,000 ppm (15%) | UEL — upper explosive limit | Above explosive range; asphyxiation risk | ☠️ Asphyxiation |
| With O2 depletion | Oxygen displacement | Dizziness, loss of consciousness, death | ☠️ Fatal |
Real Incident Cases — CH4 Explosions and Asphyxiation
Case 1: Methane Explosion in Sewage Digester (2017, South Gyeongsang Province)
An explosion occurred when accumulated methane gas in a sewage plant digester in South Gyeongsang Province came into contact with an ignition source during inspection work, causing severe burns to one worker. The CH4 concentration had entered the explosive range, but no gas measurement was conducted before entry. (Source: Ministry of Employment and Labor — Major Accident Case Studies, 2017)
Case 2: Biogas Pipe Leak Explosion at Food Waste Facility (2020, South Chungcheong Province)
At a food waste treatment facility in South Chungcheong Province, biogas (primarily CH4) leaked from a pipe joint and ignited, damaging part of the facility and injuring two workers. No fixed gas detector was installed, preventing early detection of the leak. (Source: Korea Gas Safety Corporation — Annual Gas Accident Report, 2020)
How WANDI EDW500 Prevents CH4 Explosions
EDW500 — IECEx-Certified 5-Gas Portable Detector
The WANDI EDW500 holds IECEx TPS 25.0057X international explosion-proof certification (Ex da ia IIC T4 Ga, Zone 0) and can simultaneously measure up to 5 gases: EX (including CH4), H2S, CO, O2, and VOC — providing comprehensive safety monitoring in biogas, sewage treatment, and landfill gas environments with a single device.
TPS 25.0057X
Simultaneous Detection
EPL Ga Certified
Prevention Scenario — If EDW500 Had Been Present
- 1Pre-entry CH4 Measurement: Measure upper air in digesters/manholes with the EDW500 before entry. Entry prohibited if CH4 LEL exceeds 10%.
- 2Triple Alarm Activation: Sound, vibration, and LED alarms trigger instantly upon LEL threshold breach — workers evacuate before any spark occurs.
- 3Simultaneous O2 Monitoring: The O2 channel continuously tracks oxygen depletion as CH4 accumulates — both hazards detected in real time.
- 4Intrinsically Safe Design: IECEx Zone 0 certification ensures the detector itself never becomes an ignition source in flammable gas environments.
EDW500 Specifications (CH4/EX Measurement)
| Specification | Details |
|---|---|
| Model | EDW500 / EDW500a |
| Detectable Gases | EX (including CH4), H2S, CO, O2, VOC — up to 5 simultaneously |
| EX Range | 0–100% LEL |
| EX Alarm Setpoints | Low: 10% LEL / High: 25% LEL (user-configurable) |
| Ex Certification | IECEx TPS 25.0057X / Ex da ia IIC T4 Ga / Zone 0 |
| Alarm Type | Audible (≥95 dB) + Vibration + LED Flash (triple alarm) |
| Battery | Rechargeable Li-Ion, 12+ hours continuous use |
| IP Rating | IP67 |