Common detection principles for gas detection doors and advantages and disadvantages

Common detection principles, advantages and disadvantages of gas detection doors:

Semiconductor
Rationale: Semiconductor gas sensors are based on metal oxide semiconductor materials. In air, when the oxidation of air changes, the conductivity of semiconductor materials changes accordingly, i.e. the metal oxide semiconductor surface changes when the gas is absorbed.
Advantages and disadvantages:
Advantages: have advantages such as low cost, simple manufacturing, high sensitivity, responsiveness, long life, low sensitivity to humidity and simple circuits.
Disadvantages: low stability and high environmental impact; In particular, each sensor is not unique in its selectivity and output parameters cannot be determined. It should not be used where there are precise measurement requirements, mainly for civilian use.

Catalyze combustion
Rationale: When aerosensitive materials (e.g. Pt thermal wire) are emitting, oxidized or oxidized combustion of flammable gases by catalysts, and thermal wire heats by combustion, which changes their electrical resistance values.
Advantages and disadvantages:
Advantages: Catalysing gas sensors selectively detect flammable gases: sensors do not react to anything that cannot burn. The small sensor is a major sensor in the field of safety detection, having a fast response rate and long operational life, and its output is influenced by temperature, humidity and pressure, which directly affects the explosive hazard of the environment.
Disadvantages: There is no selectivity within the flammable gas range. Sensors are toxic, work in dark fires and are at risk of fire explosions. Most elements of organic vapour are toxic to sensors.

Note: Catalytic combustion detection is conditional and requires assurance that sufficient oxygen is present in the detection environment. In an aerobic environment, this detection method may not detect any flammable gases.
Note: Some lead compounds (especially tetraethyl lead), sulphur compounds, silicon compounds, phosphorus compounds, hydrogen sulfide and halogenated hydrocarbons may poison or inhibit sensors. If the environment being tested contains attractive substances, the sensor containing anti-attractive substances should be indicated in the contract or selected.

Electrical chemistry
Rationale: The electrolyte within the sensor reacts with the target gas, producing a telecommunications signal that is proportional to the concentration of the gas.
Advantages and disadvantages:
Advantages 1: The work temperature range is wide. (c) Wide-scale measurements. High sensitivity 4. Linear output 5. Selectively good.
Disadvantages: Short lifespan, limited shelf life, short lifespan, non-earmarked, vulnerable to interference, poor linearity, and wetness impact accuracy in a very dry or high concentration of gas.
Note: Some sensors require a bias between electrodes. The sensor stability takes 30 minutes to 24 hours and three weeks to maintain stability.
Note: Most toxic gas sensors require a small amount of oxygen to maintain normal functions. For this reason, there is a vent on the back of the sensor. It is recommended that HRBEST be used for re-examination in applications using anaerobic background gases.
Note: High humidity and drought affect the life of sensors. An instant pressure change may result in instant sensor output or may result in an erroneous alert state.

Non-dispersible infrared (NDIR)
Rationale: Because of the different degrees of ingestion of infrared waves by different gases, gases can be detected by measuring the infrared insulation wavelength.
Advantages and disadvantages:
Advantages: high reliability, selectivity, accuracy, non-toxicity, low environmental disturbance, long life in service and non-oxygen dependence.
Disadvantages: High-impact humidity and limited detection of gases. The main uses are currently used for methane, carbon dioxide, carbon monoxide, sulphur hexafluoride, sulphur dioxide, hydrocarbons, ammonia, etc.

PID photoion
Rationale: PID consists mainly of ultraviolet light sources and ion chambers. The ion chamber has a positive-negative electrode, which forms an electric field. In UV light, the gas to be measured will ionize, generate positive and negative ions, create currents between electrodes, and magnify and output signals.
Advantages and disadvantages:
Advantages: high sensitivity, no poisoning problem, fast response time, high sensitivity.
Disadvantages: High-impact humidity, short-lived UV lamps and high prices.