The Critical Role of Toxic Gas Monitors in Protecting Workers and Facilities

Electrochemical gas sensors are vital in detecting harmful gases and require regular maintenance to ensure safety and operational efficiency.

• By Aravind J Renganathan, Shriram Deshpande
• Oct 09, 2024

Toxic and combustible gas monitors are essential safety devices that ensure safety in commercial or industrial operations. These devices detect the presence of harmful and flammable gases in a specific area and notify when the concentrations reach dangerous levels.

The primary component used in the gas detection device for sensing is the sensor. The function of the sensor is to detect the gases and convert them into electrical signals (typically, the higher the concentration levels in an area, the higher the electrical signals). The signals are then relayed to the primary device, and the device in turn uses multitudes of subsequent systems to notify the users (e.g., through sounding an alarm, sending a digital text or e-mail notification).

Based on these working principles, there are various types of sensors available in the marketplace. The most common used in the industry are electrochemical sensors, catalytic sensors, infrared sensors and photoionization sensors. Let’s briefly discuss the most commonly used electrochemical sensor, their working principles, and recommended maintenance guidelines to ensure the safety of the people, the property and the bottom line.

Electrochemical Sensors

Electrochemical gas sensors measure the concentration of a target gas by oxidizing or reducing the target gas at an electrode and measuring the resulting current. A basic electrochemical cell typically contains three main components. First, there are two electrodes, one anode and one cathode. The anode is the point where the current enters the electrode, and the cathode is the point where the current leaves the electrode. Second, there is an electrolyte, which facilitates the cell reaction and carries the ionic charge across the electrodes. Finally, a gas permeable membrane covers the sensing electrode and is used to control the amount of gas molecules reaching the electrode, while also filtering unwanted particulates.

An industrial electrochemical sensor usually contains 3 electrodes (sometimes even 4)—a reference electrode in addition to the anode and the cathode—in contact with the electrolyte. As the name suggests, this electrode provides the reference for the potential measurements.

Electrochemical Sensors – Working Principle

Depending on the applications, electrochemical sensors detect and measure various gases, including O2 (Oxygen), CO (Carbon Monoxide), NO2 (Nitrogen Dioxide) and SO2 (Sulphur Dioxide).

The housing membrane allows gas to pass into the sensor through the capillary diffusion barrier. An electrochemical reaction (oxidation or reduction, based on the type of gas) occurs when the gas reaches the sensing electrode. This reaction initiates a flow of electrons (i.e., a current) between the sensing electrode and counter electrode. An oxidation reaction moves electrons from the working electrode to the counter electrode, while a reduction reaction causes electrons to move from the counter electrode to the sensing electrode. In either case, the electrical current generated is proportional to the concentration of the target gas. This current is then amplified and processed according to the calibration to give the user a reading in either parts per million (PPM) or percentage volume. If no target gas is detected, most electrochemical sensors indicate a reading of zero. To improve the performance of the sensor, a reference electrode is introduced to maintain a fixed voltage value on the sensing electrode.

Recommended Maintenance Guidelines

For an effective and reliable operation of a toxic gas detector, it is imperative to ensure periodic inspection and regular maintenance of the device. Here are some recommendations on maintenance guidelines for an electrochemical toxic gas sensor.

• Inspect the gas detection device at least once every 6 months. Visually inspect at regular intervals to ensure optimum operating condition (no breakage, sensor filter not blocked or clogged, etc.). Clean the exterior with a soft, damp cloth. Do not use solvents, soaps or polishes. Do not immerse the monitor in liquids.
• Keep an accurate maintenance log including all maintenance activities performed. Calibrations, gas tests and occurrences must be maintained for the proper service of this product. Contact the manufacturers to ensure any calibration devices, including gases and spare parts, are available for timely maintenance and replacements.
• Understand that electrochemical sensors have a shelf life. The shelf life varies depending on a number of factors, such as the gas it detects, constant exposures at higher levels and operating conditions (temperature, humidity, etc.). The typical lifespan of an electrochemical gas sensor is usually 2 to 3 years. Depending on the type of gas detection and the manufacturer’s specifications and designs, the sensor lifespan will vary. Also, do not expose the sensor to high-pressure water spray or any solvents. Contact your manufacturer to source replacement sensors on time. Many manufacturers also provide contracts that cover sensor replacements and ship them out timely as per the requirements.

Gas detector devices have also recently become smart connected devices. These offer convenient upgrades that include, notifications about regular maintenance, storing the maintenance logs, etc. Contact the manufacturers to learn more about these smart devices.