Matters Needing Attention in the Use of Gas Detectors
① Regular Calibration and Testing Like other analytical testing instruments, toxic and hazardous gas detectors adopt the relative comparison method for measurement. The instrument is first calibrated with zero gas and standard concentration gas, and the standard curve is stored inside the device. During measurement, the instrument compares the electrical signal generated by the target gas with that of the standard gas to calculate the accurate concentration value. Therefore, frequent zeroing and regular calibration are indispensable to ensure measurement accuracy.
It should be noted that although most gas detectors allow sensor replacement, different sensor probes cannot be arbitrarily matched. Whenever a probe is replaced, sufficient activation time for the new sensor is required, followed by full recalibration of the detector. It is also recommended to perform a response test with standard gas before each use to ensure reliable protective performance.
② Detection Interference Between Different Sensors Generally, each sensor is designed for a specific target gas, yet no gas detector can achieve absolute exclusive selectivity. When selecting a gas sensor, it is necessary to fully understand cross-interference from other gases to guarantee accurate readings for the measured substance.
③ Service Life of Different Types of Sensors All gas sensors have a limited service life. For portable devices:
LEL sensors have the longest lifespan, approximately 3 years;
PID photoionization detectors last 4 years or longer;
Electrochemical specific gas sensors have a shorter service life of 1 to 2 years;
Oxygen sensors have the shortest lifetime, roughly 1 year.
The service life of electrochemical sensors is mainly determined by the evaporation of internal electrolyte. Sealing and storing them in a low-temperature environment during long-term inactivity can extend their lifespan to a certain extent. Fixed detectors feature larger housing and generally longer sensor service life. Sensors shall be inspected periodically, operated within their valid period, and replaced promptly once they fail.
④ Concentration Measuring Range of Detectors Every toxic and hazardous gas detector has a fixed measurable range. Accurate results can only be obtained within the rated range. Long-term over-range measurement may cause permanent damage to the sensor.
For example, an LEL detector will suffer irreversible burnout if exposed to an environment exceeding 100% LEL for any length of time. Toxic gas sensors will also be damaged under prolonged high-concentration exposure. Accordingly, if a fixed detector triggers an over-limit alarm during operation, cut off the measuring circuit immediately to protect the sensor from permanent failure.
