LELsensoren

LELsensoren, or LEL sensors, are devices that monitor the concentration of flammable gases and vapors in air relative to their lower explosive limit (LEL). The LEL is the minimum gas concentration by volume in air that can ignite under normal conditions. LEL sensors typically present readings as a percentage of the LEL, for example 0% means no detectable flammable gas above background levels, while 100% LEL corresponds to a concentration at which ignition is possible.

Most LEL sensors rely on one of a few core technologies. Catalytic pellistor sensors detect flammable gases by catalytic oxidation on a heated platinum coil, causing a change in electrical resistance. They respond to a wide range of hydrocarbons but require oxygen and can be poisoned by certain contaminants. Infrared (NDIR) sensors measure gas concentration by absorbance of infrared light at characteristic wavelengths and offer gas-specific, robust operation, though at higher cost and with optical window requirements. Electrochemical sensors are commonly used for toxic gases and oxygen and are less typical for direct LEL measurement; some fixed systems approximate LEL readings via calibration against a representative gas, but the principle is different from pellistors or IR detectors.

Detectors usually provide a 0–100% LEL output and trigger alarms at predefined thresholds (for example, 10–20% LEL for warning, 20–40% LEL for alarm). They require regular calibration with a calibration gas and periodic maintenance to ensure accuracy. LELsensoren are widely used in industrial safety, oil and gas facilities, mining, and confined-space monitoring to prevent ignition hazards and protect personnel. Limitations include cross-sensitivity to different fuels, environmental effects on response, and sensor aging.