Gas detection sensor technologies
Many gas detection sensor technologies ensuring accurate measures are available for each gas and any gas category. There are mainly 5 kinds of gas detection sensors: catalytic, electrochemical, semiconductor, infrared absorption and photo-ionization lamp (PID) sensors.
Catalytic bead gas detection sensors are the most commonly used units for detecting combustible gases and vapors. It measures the concentrations in percentage of the LEL (lower explosive limit which is the threshold where gas can explode). The catalytic sensor technology is also well suited for hydrocarbons, solvents, alcohols and some volatile organic compounds.
The catalytic combustible gas detection sensor has yet some faults:
- Premature wear in case of frequent or permanent monitoring of combustible gases (even with low LEL values)
- High sensitivity to poisons (silicon- or lead-based compounds) and to inhibitors (Astatine, Bromine, Chlorine, Sulfur dioxide, Fluorine, Hydrogen sulfide, Iodine)
- Sensors can detect a potential risk of explosion but can't sort the issued gas.
- Can operate only if the oxygen rate is above 10%
IR sensors are primarily used for monitoring some combustible gases (when there is an IR curb) and CO2 (carbon dioxide). This type of infrared gas destection sensor is more expensive than the catalytic sensor technology but has several real technical benefits for portable gas monitors and fixed gas detectors:
- Extended runtime
- High speed response time
- Reduced regular maintenance
- Immune to catalytic poisons
- Operates even in atmospheres without oxygen
- No impact of the concentration on the sensor lifetime (even at 100% volume)
Photoionization detector lamp (PID sensor)
A PID sensor (or photoionization sensor) is mainly used as a tvoc sensor (total volatile organic compounds). This particular technology is immune to poisons and high concentrations. This gas detection sensor technology can monitor many gases on a wide scale (from ppb to one thousand ppm) but has two major drawbacks :
- it is not specific to a particular gas
- it is considerably affected by relative humidity
Electrochemical gas detection sensor
Among all types of sensors, the electrochemical gas sensor is the most widespread technology. This sensor is designed for the detection of toxic and asphyxiating gases and for oxygen (oxygen meter). This type of gas detection sensor covers a large panel of gases with many measuring ranges. An electrochemical sensor needs a minimal concentration of oxygen to operate. It however has two main drawbacks:
- Electrochemical sensors are very sensitive to interference from other gases which can distort the measurements
- Sensor lifetime is shorter than other sensor technologies
Semiconductor gas sensor
Semiconductor sensors are mainly used to detect refrigerant gases (freons) and some solvents. This type of gas detection sensor require a minimal oxygen rate to operate.