How to Select Suitable Gas Alarms and Gas Detectors
With the advancement of manufacturing technology, portable multi-gas (composite) detectors have become a new viable option. This type of detector can be fitted with multiple sensors for different inorganic and organic gases on a single main unit, featuring compact size, light weight, fast response and simultaneous digital display of multiple gas concentrations. More importantly, a pumped composite gas detector is more cost-effective and user-friendly than purchasing multiple individual diffusion-type gas detectors separately. When selecting such devices, it is advisable to choose models equipped with an independent on/off switch for each sensor. This prevents the malfunction of one sensor from interfering with the operation of others. In addition, instruments with an intelligent pump design and pump stall alarm function offer higher safety, which can avoid pump blockage caused by water ingress and other foreign matters.
Precautions for the Operation of Gas Detectors
① Conduct regular calibration and testing Like other analytical instruments, toxic and harmful gas detectors adopt the relative comparison method for measurement. The instrument is calibrated with zero gas and standard concentration gas in advance, and the generated standard curve is stored in the internal memory. During measurement, the device compares the electrical signal generated by the target gas with the signal of the standard gas and calculates the accurate concentration value. Therefore, zeroing the device frequently and performing periodic calibration are essential to guarantee measurement accuracy. It should be noted that although most gas detectors support replaceable sensors, one instrument cannot be arbitrarily matched with different sensor probes. Every time a probe is replaced, a sensor activation period is required, followed by a full recalibration of the detector. It is also recommended to perform a response test with calibration gas before each use to ensure reliable protective performance.
② Guard against cross-interference among different sensors In general, each sensor is designed for a specific target gas, yet no detector achieves complete absolute selectivity. When selecting a gas sensor, fully investigate the interference from other gases to ensure accurate measurement of the designated substance.
③ Keep track of the service life of various sensors All gas sensors have a limited service life. For portable devices, LEL sensors have the longest lifespan of approximately 3 years; photoionization (PID) detectors can last 4 years or more; electrochemical sensors for specific gases have a shorter service life of 1 to 2 years; oxygen sensors have the shortest lifetime of around 1 year. The service life of electrochemical sensors depends on the evaporation of internal electrolyte. Sealing and storing the sensor in a low-temperature environment during long-term idle periods can moderately extend its usable life. Fixed detectors have a larger structure and correspondingly longer sensor service life. Inspect sensors regularly, use them within their validity period, and replace them immediately once they fail.
④ Comply with the concentration measuring range of the detector Each toxic and harmful gas detector has a fixed rated measurement range. Accurate readings can only be obtained when the gas concentration falls within the specified range. Long-term over-range measurement will lead to permanent irreversible damage to the sensor.
