April 21, 2024
gas sensor or smoke alarm

Gas sensors play a role, in detecting the presence of gases in environments. They are a part of safety systems alerting people to gas leaks and enabling them to take necessary precautions. Gas sensors find application in industries and settings including oil rigs, manufacturing processes, firefighting and even our homes. Have you ever wondered how gas sensors actually work? Are they active or passive? In this article we will delve into the types of gas sensors their methods of detection well, as the advantages and disadvantages associated with each type.

Understanding Gas Sensors

Gas sensors are devices created to identify the existence of gases in a given space. They have the capability to detect a spectrum of gases such, as those that are flammable, combustible, toxic or even those that can cause oxygen depletion. The main objective of gas sensors is to guarantee the well-being and security of people by providing warning systems in the event of a gas leakage.

Are they active or passive? Gas sensors can be categorized into both types; active sensors and passive sensors. Each type utilizes a detection method and functions in a way to detect the presence of gases. Let’s delve further into each type to gain an understanding of their mechanisms and characteristics.

Active Gas Sensors

Active gas sensors use sources of energy to detect and measure the concentration of gases. These sensors actively engage with the gas molecules, in their surroundings. Provide readings in real time. There are types of gas sensors, such, as electrochemical sensors, catalytic sensors, photoionization (PID) sensors, infrared (IR) sensors, galvanic sensors and semiconductor sensors.

Electrochemical Sensors

Electrochemical sensors have applications, in identifying gases like carbon monoxide (CO) hydrogen sulfide (H2S) ammonia (NH3) chlorine (Cl2) nitrogen dioxide (NO2) and sulfur dioxide (SO2). These sensors function by enabling the passage of gas through a membrane, towards an electrode. At the electrode the gas undergoes. Reduction, producing a current that corresponds to the gas concentration and enables measurements.

Catalytic Sensors

Catalytic sensors are created to identify gases. They include platinum wire coils embedded in a bead of alumina connected electrically in a Wheatstone bridge circuit. The active bead holds a catalyst that facilitates the oxidation of compounds resulting in a modification, in the resistance of the bead. The difference in voltage, between the passive beads indicates the level of gases present.

Photoionization (PID) Sensors

PID sensors prove to be highly efficient, in the detection of compounds (VOCs) toxic gases and vapors. The operational principle of these sensors involves exposing the gas sample to high energy photons typically falling within the ultraviolet (UV) range. As the gas molecules interact with this radiation they undergo a loss of an electron leading to the generation of positively charged ions. These ions resulting current is then utilized for measuring the concentration of the gas, which is subsequently displayed as parts, per million (PPM).

Infrared (IR) Sensors

Infrared sensors have the ability to detect hydrocarbons and other gases that are active in the spectrum such as water vapor and carbon dioxide. These sensors function by directing radiation through a known amount of gas and measuring how much energy is absorbed at wavelengths. The variation, in energy, between the absorbed wavelengths and reference wavelengths is directly related to the concentration of the gas. Infrared sensors are known for their accuracy and dependability which makes them well suited for a range of applications.

Galvanic Sensors

Galvanic sensors are mainly utilized for monitoring the oxygen levels in the air. These sensors utilize an electro fuel cell, which involves the consumption of oxygen to generate output through a chemical reaction. While galvanic sensors offer measurements of oxygen their functionality is restricted solely to detecting oxygen levels.

Semiconductor Sensors

Semiconductor sensors have a range of applications. Can effectively detect various gases, such, as hydrogen, oxygen, alcohol and even hazardous gases, like carbon monoxide (CO). These sensors work by assessing the alterations in resistance that occur when gas directly interacts with the semiconductor material. The extent of resistance change corresponds to the concentration of the gas being measured enabling precise readings.

Passive Gas Sensors

Passive gas sensors in contrast, to ones don’t require energy sources. They work by detecting gases using the temperature differences between the surrounding environment and the gas cloud. While active sensors provide real time readings passive sensors are a cost low power option, for specific applications.

Passive gas sensors can be categorized into two main types: non-dispersive infrared (NDIR) sensors and temperature-based sensors.

Non-Dispersive Infrared (NDIR) Sensors

NDIR sensors work based on the principle of gas molecules absorbing wavelengths of rays. By measuring the variation, in the amount of absorbed radiation these sensors can accurately determine the concentration of gases. NDIR sensors are known for their accuracy. Are commonly used to detect various gases, such as carbon dioxide (CO2) and refrigerant gases. They find application, in industrial and environmental monitoring purposes frequently.

Temperature-Based Sensors

Temperature based sensors utilize the temperature variation between the surrounding environment and the gas cloud to identify the existence of gases. The temperature of the gas cloud is affected by the particular gas being detected enabling a means of measurement. Although temperature based sensors are not as accurate as sensors they provide a cost option, for specific applications that don’t require instantaneous readings.

Choosing the Right Gas Sensor

When choosing a gas sensor it’s important to take into account the gas you want to measure and the requirements of your application. Different types of gas sensors have their advantages and limitations. You should consider factors, like accuracy, power usage, lifespan, response time and size to make sure you get the performance.

Here is a summary of the characteristics of each gas sensor type:

Gas Sensor Types

It’s worth mentioning that gas sensors can be combined to create a gas detection system. By using types of sensors we can detect a range of gases and improve the accuracy and dependability of gas detection systems.


Gas sensors play a role, in maintaining safety and identifying harmful gases in different environments. Whether they are active or passive gas sensors provide information that enables people to respond quickly in the event of a gas leak.

Active gas sensors, such as catalytic, PID, IR, galvanic and semiconductor sensors offer real time measurements and accurate detection of gases. On the hand passive gas sensors like NDIR sensors and temperature based sensors offer a cost energy efficient alternative for certain applications.

When choosing a gas sensor it’s important to consider factors such as the gas to be measured, application requirements and the characteristics of each sensor type. By selecting the gas sensor for their needs industries can ensure safety and safeguard individuals, from potential gas hazards.

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