How Do Toxic Gas Detectors work?

Introduction to Toxic Gas Detection:

Factories that produce chemicals, fertilizers and petroleum products, or factories that produce oil and natural gas, must deal with various toxic chemicals in their daily operations. Many of these toxic chemicals are in the form of gases or vapors. This article will provide a brief overview of the various toxic gas detectors used to detect these toxic substances.

The example used would be a detector for detecting hydrogen sulfide gas, which is highly toxic. These detectors are also known in industry simply as H2S detectors.

Why are toxic gas detectors used?

Toxic Gas detectors are mainly used for monitoring the presence harmful gases and vapors. These detectors are also referred to by many people as toxic gas monitors; both terms are interchangeable and mean the same.

toxic gas detectors

These gas monitors enable a worker present in the plants that have these toxic gases, to protect himself from exposure. One of these ( commonly found harmful chemicals) is Hydrogen Sulfide. This gas that smells like rotten eggs, is even in low concentrations, extremely toxic. At lower levels of concentration the human nose can sense this as a “bad smell”, however, paradoxically at higher level, there is no sense of any smell, as the human nose gets desensitized. So a worker who accidentally walks into a Hydrogen Sulfide atmosphere can get literally knocked down, without finding anything amiss! Hence, it is critical that good, working, toxic gas monitors be used in such places to protect workers from accidental exposure.

For example, consider a process vessel in a chemical processing plant that normally contains Hydrogen sulfide gas. In normal operations this vessel will be tightly sealed and no Hydrogen Sulfide can escape. However, in case the vessel sealing does not work (for example, a flange on one of the inlet pipes leaks), then, it is likely that this Hydrogen Sulfide gas can leak out and harm the workers who operate the vessel or are in the nearby area.

To prevent this from happening, a toxic gas detector that can measure Hydrogen Sulfide gas, even in small concentrations, is mounted near the vessel. Whenever it detects a dangerous level of Hydrogen Sulfide, it will give out a warning alarm.

Types of toxic gas detectors

There are various technologies that are used to make toxic gas detectors. Also these instruments are available in various forms, like fixed, portable or pocket types. There are different sensors used to detect different types of toxic gases. Some types of sensors can detect a variety of different gases, others can detect only one type of gas.

Fixed toxic gas detectors

Fixed toxic gas detectors

These are very commonly found in large manufacturing plants and similar facilities. Each fixed gas detector is mounted at a place where it is very likely to sense the toxic gas, in case of a leak. The detector may or may not have a local display that shows the concentration of the gas. Each detector is connected via cables to a central system, that is monitored by plant personnel. In case of a leak this panel will generate alarms to warn the operators about the dangers and may also carry out any interlock actions (like triggering closure of valves or initiating a shutdown).

Portable toxic gas detector

Portable toxic gas detectors

Portable gas monitors are used by workers to sweep a work area, to know if there is any toxic gas lurking around the area. These detectors are also called as handheld gas detectors. These detectors are normally battery powered and have a display with a buzzer and lights, to warn the operator, in case a dangerous level of toxic gas is detected. They may have their own inbuilt sampling pumps, to draw air into the sensor. Some variants also store data, to calculate time weighted average values, peak values and other important data for regulatory compliance.

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