Introduction to Operation, Maintenance and Servicing of Portable Gas Detectors
Portable gas detectors are popular new‑generation gas‑detection devices. They keep improving along with the maturity of gas‑detection technology. According to customer requirements and application sites, one main unit can be equipped with multiple required sensors (inorganic / organic) to realize single‑gas and multi‑gas detection.
Portable gas alarms feature compact size, light weight, fast response and simultaneous multi‑gas concentration display.
A. Regular Calibration and Inspection during Operation
Many gas detectors support replaceable sensors. However, this does not mean that different sensor probes can be arbitrarily fitted to one detector. Whenever a probe is replaced, certain sensor activation time is required, and the instrument must be recalibrated. In addition, it is recommended to perform response test with standard gas before use to ensure the protective function of the instrument.
Like other analytical instruments, combustible‑gas alarms and toxic‑gas alarms adopt the relative comparison measurement method. The instrument is calibrated with zero gas and standard‑concentration gas, and the standard curve is stored inside. During measurement, the instrument compares the electrical signal generated by target gas with that from standard gas, and calculates accurate gas‑concentration values.
Therefore, frequent zero‑adjustment and regular calibration are indispensable to guarantee measurement accuracy.
B. Be Aware of Cross‑Interference among Different Sensors
Although composite gas detectors can measure multiple gases simultaneously, portable gas detectors cannot realize arbitrary combination of toxic and harmful gases. Generally, each sensor is designed for a specific target gas, yet no gas sensor is completely free from cross‑interference. When selecting a gas sensor, possible interference from other gases shall be fully understood to ensure accurate measurement for the target gas.
C. Pay Attention to Service Life of Sensors in Portable Gas Alarms
All gas sensors have limited service life. For portable instruments: the LEL sensor usually lasts about 3 years; the photoionization detector (PID) can serve 4 years or longer; specific‑gas electrochemical sensors have relatively short service life of 1‑2 years; oxygen sensors have the shortest lifetime of approximately 1 year.
The service life of electrochemical sensors depends on electrolyte evaporation. When not in use for a long time, sealing and storing them in a cool environment can extend service life to some extent. Fixed instruments have relatively larger size and longer sensor service life.
Sensors shall be inspected regularly and used within their valid period. Replace sensors promptly once they fail.
D. Observe the Measuring Range of Gas‑Detection Instruments
Each toxic‑harmful gas detector has its fixed measuring range. Accurate measurement can only be guaranteed within this range. Long‑term measurement beyond the measuring range may damage the sensor. For example, an LEL detector may be permanently burnt if exposed to atmosphere over 100 %LEL. Toxic‑gas detectors will also be damaged under long‑term high‑concentration exposure. Accordingly, once over‑range alarm occurs for fixed instruments, the measuring circuit shall be shut down immediately to protect the sensor.
