Fire & Gas

Gas Detectors Practical Problems and Troubleshooting

Gas Detectors Pr actical Problems and Troubleshooting 2

What is a Gas Detector?

  • Gas detectors are essential safety devices used in various process industries to detect the presence of hazardous gas present in the environment. 
  • A gas detector is an instrument to sense the presence of the gas.
  • A gas detector generates an audible alarm signal to alert the plant operators working at that location informing leakage of gas.
  • Gas detectors detect combustible, flammable, toxic gases, & oxygen depletion.
  • A gas detector determines the level of various gases present in atmospheric air.
  • Gas Detectors are used as a safety barrier in every process industry.
  • These Gas detectors must be kept online every time for accurate monitoring and control of any gas leakage.
  • Ideally, used gas detectors are Cl2, H2S, CO, & HC     (Hydro carbon).

What are the kinds of gas detectors?

Gas detectors are classified into four main types: 

  1. Electrochemical Sensors, 
  2. Catalytic Sensors, 
  3. Infrared Sensors, & 
  4. Photoionization Sensors. 

Basically, these Gas detectors are classified into two categories,

  1. Portable Gas Detector, 
  2. Fixed Gas Detector.

State the common reasons for the inaccurate functioning of the Gas Detector.

  1. Environmental Affects
  • Water, dirt, and dust may have a detrimental effect. 
  • These physical consequences may prevent gases and vapors from entering the sensor chamber, inhibiting gas detection. 
  • This can be within the sensor area, the sampling pump, or the sample lines.  
  • Extreme temperature, humidity, or pressure conditions can impact the performance of gas detectors. Operating the detector outside its specified environmental range can result in inaccurate readings.
  1. Physical Affects
  • Dropping and other kinds of violence may lead the instrument to improper or effective functioning.
  • At least, it might affect the capacity of the gas detector for accurate measurement 
  1. Gas Exposure
  • As a result of high gas exposure, the calibration curve of the sensor might be affected leading to incorrect or incorrect measurements. 
  • Excessive high concentrations might make the sensor ineffective in measuring gas. In addition to this, most of the gas detectors may fail without presenting any kind of notification. 
  • In reality, most of the gas detectors      offer      a zero indication on the meter reading, indicating that they are operational when they are not.
  1. Catalytic Sensors Affected by Poisons and Inhibitors
  • Silicone-based chemicals and airborne lead are capable of damaging catalytic combustible gas detectors, these damage the gas detector. 
  • Inhibitors like Sulfur compounds and chlorinated chemicals minimize the sensor response or ability to measure.
  • This slows down the sensor response, & may minimize the capacity of the detector to measure certain gases.
  • Due to reduced sensitivity, it may be possible to test pentane but not methane.
  • Exposure to certain gases or chemicals can poison or damage the gas sensor, rendering it inaccurate or non-responsive to specific gases. Sensor poisoning may require sensor replacement.
  1. Electrochemical Sensor Poisoning
  • Here, the gas detector may be poisoned by other gases that are penetrated into the detector chamber and react with the electrode catalyst. Some gases or substances present in the environment can interfere with the gas detector’s sensor, leading to false readings or reduced sensitivity. Cross-sensitivity to other gases is a common issue with some sensors.
  1. Temperature Affect
  • The stacking of instruments in an environment of high or low temperature may affect the capacity of the detector for accurate measurement.
  1. Moisture Condensing
  • Moisture Condensing within the oxygen sensors occurs due to moisture condensation in the capillary tube of the sensor. 
  • This Moisture Condensing leads to damage to the sensor.
  1. Calibration Drift
  • Most of the gas detectors get drifted over time, 
  • Calibration restores the gas detectors into equilibrium to deliver readings with the highest accuracy.

9. Incorrect Installation: 

  • Poor placement or improper installation of the gas detector can hinder its performance.

10. Lack of Maintenance: 

  • Neglecting routine maintenance tasks like sensor cleaning, filter replacement, and calibration can result in inaccurate readings.

Gas Detector Troubleshooting

  • During the troubleshooting period of the gas detector, it is essential to follow the safety procedures recommended by the manufacturer to maintain the reliability and accuracy of the gas detector.
  • Additionally, speak to qualified technical support in case of continuous problems that cannot be solved through basic troubleshooting.
  • Like any electronic equipment, gas detectors can encounter practical problems and require troubleshooting to ensure their proper functioning. 
  • Some common practical problems in gas detectors & troubleshooting these problems are shown below.

Gas Detectors Practical Problems

  • Inspect the screen of the gas detector in case it fails to respond. 
  • If the display is powered off, verify the voltage of the gas detector. 
  • If there’s no voltage, inspect the fuse in the marshaling cabinet. 
  • If the fuse is okay, investigate the barrier or isolator in the marshaling cabinet. 
  • If everything seems to be in order, verify the links between the cables in the field, junction box, and marshaling cabinet. 
  • If the connectors are correct, inspect      the cable’s status. Assess the resistance of the cable to determine its condition. 
  • If the cable appears to be defective, exchange      it with a spare pair.
  • If the gas detector still does not turn on, examine the connection in the terminal block of the gas detector. 
  • The connections made within the junction box of the gas detector may be wrong. 
  • Check & verify the connections by referring to the vendor’s reference manual or handbook. Since the majority of gas detectors come with three wires. 
  • As a result, confirming connections is essential. 
  • Examine the sintered filter over the sensor. Environmental dust or dirt might jam the filter. Clean the filter with an appropriate device, such as a brush or dry air. Inspect the sensor’s status as well. If you notice dust or dirt on the sensor, clean it as well. Reinstall the sintered filter and sensor. With the calibration gas, test the reaction.
Gas Detectors Practical Problems and Troubleshooting 2
  • If the gas detector doesn’t respond then analyze the connections on either side of the probe to the terminal block. A loose connection or defective connection may produce these kinds of issues.
  • If the gas detector indicates a non-zero value in the absence of gas, or when there is no leakage. Then energize the gas detector. If the gas detector is still displaying output, the gas detector needs to be calibrated. 
  • If the problem doesn’t get solved by following the above procedure, then replace the sensor & examine the response of the isolated sensor with another transmitter. 
  • Now replace the transmitter, if it doesn’t work even after sensor replacement use the previous sensor if the sensor response is good with the transmitter.
  1. False Alarms:


The gas detector activates an alarm even in the absence of the target gas.


Examine the sensor for physical damage or the presence of pollutants or toxic waste.

Verify the alarm threshold value of that detector is set accurately for the specific gas being monitored.

Check for sources of intervention or cross-sensitivity with other gases.

Confirm proper calibration and sensitivity settings.

  1. Zero Calibration Issues:


The gas detector is unable to read zero exactly, giving rise to inaccurate readings, or false alarms.


Ensure that the gas detector is clean and free from pollutants or toxic waste.

Check for any obstructions in the sampling path of gas.

  1. Span Calibration Issues:


During span calibration, the gas detector is unable to respond to a known concentration of gas accurately.


Examine that the calibration gas is stored properly within the expiration date 

Investigate the flow rate & regulator settings of the calibration gas. 

Ensure the calibration gas suits the type and concentration of the target gas.

  1. No Response to Gas:


The gas detector is unable to detect the presence of the target gas and acknowledge it.


Ensure the poisoning in the gas detector that occurs due to exposure to certain chemicals.

Clean the gas detector frequently, or replace it if not working properly.

Ensure the concentration of the gas lies within the measurement range of the detector.

  1. Drifting Readings:


The observed readings in the gas detector are drifting continuously making it hard to generate accurate measurements.


Conduct the checks and calibration of the gas detector regularly to confirm the gas detector stays within specified limits of accuracy.

Check the power source of the gas detector since the fluctuation in the voltage signal might affect the stability of the gas detector.

Check for environmental factors such as temperature and humidity that might influence sensor performance.

  1. Fault Indications in Gas Detector:


The gas detector indicates an error message or faulty signal in a sensor.


To solve this error refer to the instruction manual provided by the manufacturer for specific explanations of the indicated error code to take and recommend      action.

Rectify the electrical connection for loose or damaged connections and make it proper. 

If the same issue exists again, speak to technical support for further assistance.

  1. Battery or Power Issues:


The gas detector is unable to switch on, or it loses power immediately.


Check the power source such as the battery or power adapter for damage or malfunction.

Replace the battery with a new or charged one in case of using a rechargeable battery by following installation instructions as per the manufacturer.

Replace the batteries with fresh ones, following the manufacturer’s recommendations.

Ensure the working of the power switch is functioning correctly.

  1. Inadequate Sampling


The gas detector might be unable to sample the air effectively which leads to readings with the lowest accuracy.


Investigate the sampling system for clogs, leaks, or obstructions.

Ensure the sampling tube is linked properly, and free from damage.

  1. Calibration Issues:     


Incorrect calibration or infrequent calibration can lead to inaccurate readings.


  1. Sensor Contamination:


 Contaminants like dust, dirt, oil, or chemical residues can accumulate on the sensor’s surface, obstructing gas detection and leading to inaccurate readings.


Clean the sensor: Follow the manufacturer’s instructions to clean the sensor carefully, removing any contaminants. Use appropriate cleaning materials that won’t damage the sensor.

  1. Gas Concentration Fluctuations:


Rapid or frequent changes in gas concentrations can challenge the detector’s response time and accuracy.


Ensure stable conditions: If possible, take readings in a stable gas environment or implement measures to minimize rapid fluctuations.

  1.  Lack of Maintenance:


Neglecting routine maintenance tasks like sensor cleaning, filter replacement, and calibration can result in inaccurate readings. 


Schedule routine maintenance: Establish a maintenance schedule for sensor cleaning, filter replacement, and calibration, and follow it diligently.

Sundareswaran Iyalunaidu

With over 24 years of dedicated experience, I am a seasoned professional specializing in the commissioning, maintenance, and installation of Electrical, Instrumentation and Control systems. My expertise extends across a spectrum of industries, including Power stations, Oil and Gas, Aluminium, Utilities, Steel and Continuous process industries. Tweet me @sundareshinfohe

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