Infrared Gas Detectors: Types, Benefits and Applications

Safety in industrial and commercial environments is paramount.

Undetected gas leaks can lead to serious accidents, health issues, and financial losses.

To combat these invisible threats, advanced technologies for gas detection are essential.

Among these, infrared (IR) gas detectors stand out as a dependable option for identifying a variety of hazardous gases. They leverage the principle of infrared light absorption to provide precise and rapid detection, making them a crucial component in modern safety systems.

Understanding How Infrared Gas Detectors Work

Let's find out how infrared gas detectors work and keep us safe. The working of infrared gas detectors depends on the type of gas sensor technology they use. Here is a general overview:

Catalytic bead sensor: This detector sensor consists of two coils of fine platinum wire coated with a catalyst. One coil is electrically heated at a high temperature, and the other is used as a reference. When combustible gas comes into contact with the hot coil, it results in a change in resistance proportionate to the concentration of the gas.

Infrared (IR) Sensors: These infrared sensors shine infrared light through the air, and this light is absorbed by various gases. Then, the detector checks how much light made it through. If some light is missing (because the gas "ate" it, I mean absorbed it), the detector knows there’s gas in the air. Later, these gases are measured to determine their accuracy and avoid any accidents.

Electrochemical Sensors: An electrochemical sensor detects gases by using a chemical reaction. When the target gas comes into contact with the sensor's electrodes (a special part inside the sensor), this causes a chemical reaction, which creates an electric signal. The magnitude of a signal identifies gases; the bigger the signal, the more gas there is.

Photoionization Detectors (PID): PID detectors use ultraviolet (UV) light to break gas molecules into smaller charged particles called ions. These ions create an electric current when they are collected by electrodes in the device. Then, the amount of current generated shows how much gas is present.

Metal Oxide Semiconductor (MOS) Sensors: These detectors use a thin layer of metal oxide to detect gases. When your sensor gets exposed to a specific gas, this gas reacts with the surface of the metal oxide, causing a change in its electrical conductivity. This change is later used by sensors to determine how much gas is present.

Key Components of an Infrared Gas Detector

Several components work together in an infrared gas detector to enable effective gas detection.

• Housing: A sturdy and durable enclosure protects the detector from harsh industrial environments. Often constructed from materials like die-cast aluminum, the housing resists corrosion and mechanical damage.
• Gas Sample Chamber: This sealed space allows the gas being monitored to flow through, enabling interaction between the gas molecules and the infrared light.
• Infrared Light Source: The detector emits infrared light at particular wavelengths chosen based on the absorption characteristics of the targeted gas.
• Infrared Detector: Positioned opposite the light source, this component senses the infrared light that has passed through the gas sample. It converts the absorbed light into an electrical signal, which is then processed to determine the gas concentration.
• Optical Filters: Certain detectors incorporate optical filters to select specific infrared light wavelengths relevant to the target gas. These filters enhance the detector's sensitivity and selectivity.
• Electronics: These process the signals from the detector, convert them into meaningful data, and manage the detector's overall operation. This includes signal processing circuits, microcontrollers, and communication interfaces.
• Output Interface: This allows the detector to transmit data to external devices like control systems or alarm panels. Output options can include analog outputs (e.g., 4- 20mA), digital outputs, and communication interfaces (e.g., RS-485, Modbus).
• Power Supply: The detector needs a power source to operate, which can be either AC or DC, depending on the model and application.

Different Types of Infrared Gas Detectors

Let's understand the different types of gas detectors and the various gases they detect:

Single Gas Detectors

As the name suggests, single gas detectors are designed to detect specific types of gases. Single gas detectors are used in environments where there's a limited risk of exposure to a particular gas.

Gases detected by single gas detectors:

Toxic gases: Carbon monoxide (CO), hydrogen sulfide (H₂S), or sulfur dioxide (SO₂).

Combustible gases: Methane (CH₄) or propane (C₃H₈).

Oxygen levels: Monitoring for oxygen deficiency or enrichment.

Multiple Gas Detectors:

Multiple gas detectors are designed to monitor multiple gases simultaneously. They are versatile, unlike single gas detectors, and are used in more complex environments. These detectors offer comprehensive safety monitoring.

Gases detected by multi-gas detectors:

Combustible gases: Methane (CH₄), propane (C₃H₈), hydrogen (H₂), and acetylene (C₂H₂).

Toxic gases: Carbon monoxide (CO), hydrogen sulfide (H₂S), ammonia (NH₃), chlorine (Cl₂), and nitrogen dioxide (NO₂).

Oxygen levels: To ensure a safe breathing environment.

Point Detection Versus Open Path Detection

Infrared gas detection devices can be categorized into point detection and open path detection systems.

Point detectors monitor gas concentration at a specific, fixed location.

On the other hand, open path detectors utilize separate transmitters and receivers to measure the average gas concentration along the path between the two points, which can extend up to 200 meters.

Often, employing a combination of both types of detectors provides the highest level of safety.

Advantages of Utilizing Infrared Gas Detectors

Infrared gas detectors offer several benefits that make them a preferred choice for many applications.

• Broad Range of Detectable Gases: IR sensors exhibit high sensitivity to a wide array of gases, including many hydrocarbons.
• Reduced Maintenance: Compared to other gas detector types like catalytic bead sensors, infrared detectors typically require less upkeep, which saves both time and resources.
• Extended Lifespan: These detectors often have a longer operational life, providing continuous and reliable monitoring over an extended period.
• High Accuracy: Infrared detectors offer high accuracy in gas detection, leading to fewer false alarms and dependable operation.
• Versatility: They can detect a wide range of gases, making them suitable for diverse industrial and commercial uses.
• Enhanced Safety: By detecting gas leaks early, infrared detectors help improve safety in workplaces and other environments where gas leaks could endanger health and safety.
• Immunity to Poisoning: Unlike catalytic bead sensors, IR sensors do not lose sensitivity due to chemical poisoning.
• Operation in Low Oxygen Environments: IR sensors do not require oxygen to function correctly, unlike traditional catalytic bead sensors.
• Remote Detection Capabilities: Certain IR technologies, like Optical Gas Imaging (OGI), can detect gas leaks from a distance, allowing for inspection of hard-to-reach areas without facility shutdown.

Limitations to Consider with Infrared Gas Detectors

Despite their numerous advantages, there are also some limitations associated with infrared gas detectors.

• Inability to Detect Certain Gases: A significant limitation is that some gases, most notably hydrogen, do not absorb infrared light and therefore cannot be detected by standard IR sensors. Also, certain other hydrocarbons and flammable gases show poor or no response on general-purpose IR sensors.
• Influence of Environmental Conditions: The output of infrared sensors can be significantly affected by high humidity, as well as changes in ambient temperature and pressure.
• Non-Linear Output: The output from infrared sensors is inherently non-linear, and response curves vary for different gas types. This necessitates characterization and calibration to a specific gas for accurate linear results.
• Potential for False Readings: In environments where multiple hydrocarbon-based gases are present, IR gas sensors, being typically gas-specific, might provide inaccurate readings.
• Performance in Extreme Environments: Harsh conditions like high humidity, fog, and ambient infrared radiation can negatively impact the performance and reliability of these sensors.
• Cost: The initial cost of IR detectors can be higher compared to catalytic detectors.

Diverse Applications Across Industries

Infrared gas detectors find widespread use in various industries where the detection of hazardous gases is critical.

• Oil and Gas Industry: Used extensively to detect methane and propane leaks during drilling, refining, and storage operations, helping prevent explosions.
• Chemical and Petrochemical Industry: Employed to monitor gases like carbon monoxide, hydrogen sulfide, and volatile organic compounds (VOCs) in plants, preventing worker exposure and minimizing environmental impact.
• Mining Industry: Crucial for monitoring flammable gases such as methane and carbon monoxide in mines, ensuring miner safety from leaks and explosions.
• Food and Beverage Industry: Utilized to monitor carbon dioxide levels, which are important for maintaining freshness and preventing spoilage during transportation and storage.
• Pharmaceutical Industry: Help maintain safe working conditions by monitoring gases like carbon dioxide in manufacturing facilities.
• Environmental Monitoring: Used to keep tabs on greenhouse gas emissions like carbon dioxide and methane, aiding in compliance with environmental regulations.

Selecting the Appropriate Infrared Gas Detector

Choosing the correct infrared gas detector requires careful consideration of several factors.

• Identify the Target Gas: Determine precisely which gas or gases need to be detected (e.g., methane, carbon dioxide).
• Assess the Environment: Consider whether the detector will be used indoors, outdoors, or in a hazardous area. Look for appropriate ingress protection (IP) ratings for resistance to dust and water.
• Determine the Concentration Range: Check that the detector can accurately measure gas concentrations within the relevant range for your application.
• Evaluate Sensor Lifespan and Maintenance Needs: Opt for a model with a long sensor life and minimal maintenance requirements to reduce operational costs.
• Consider Portability: If mobile detection is needed, select a compact, lightweight, and user-friendly model.
• Check Response Time: A fast response time is vital for safety, as it allows for quicker detection of leaks.
• Verify Compliance and Certifications: Make certain the detector meets relevant industry standards and certifications, such as ATEX or UL.

Conclusion

Infrared gas detectors are indispensable tools for industries where safety and environmental protection are top priorities.

By providing continuous, real-time monitoring, these detectors play a crucial role in minimizing risks, preventing accidents, and ensuring compliance with regulations.

While it is important to acknowledge their limitations, the numerous advantages and wide range of applications solidify infrared technology as a cornerstone of modern gas detection systems.

For businesses aiming to improve workplace safety through dependable detection solutions, infrared gas detectors present a compelling option.