Gas Detection Overview

Gas detection is critical to protecting human life and property in our industrial complex. In this article, I will discuss general gas detection.

What is a gas detector?

A gas detector is a device that detects the presence of gases in an area, often as part of an industrial safety system.

A gas detector can alarm operators where the leak occurs, allowing them to leave.

Why gas detection is important?

Gas Detection is often necessary or desirable for several reasons. Here are four reasons why we need gas detection.

1: Safeguard life and property

A well-designed gas detection system will provide early warning of hazardous conditions, providing an opportunity for execution and notification for early re-entry for workers.

It will provide the time for intervention and correction and help trigger the facility, water mist, and fire suppression system.

2: Local fire safety codes and insurability

Most local fire codes and insurance companies will require you to have some gas and fire presentation systems in place to ensure the safety of workers.

3: Address real and perceived safety concerns

Most plants will emit some gas as a by-product of the production process. For example, the cells will produce hydrogen if you have a battery charging room.

As we know, hydrogen gas is toxic and flammable, so in this case, you will need a detector and controller to help with hydrogen monitoring in the facility.

4: Required by law

In most countries, some laws obligate manufacturers or certain industries to have a gas detection system in place.

Before installing any system, I recommend contacting a security firm in your local area so that they can assess what type of gas leaks can be found in your facility, and they will be able to recommend what system is suitable for you.

Also, you can call some of the gas monitoring instrument manufacturers and get their expert opinion.

Here are some gas detection basics

  • 1ppm is one part in 1,000,000 parts. Generally, ppm (parts per million) is the lowest unit of measurement 10,000ppm = 1% by Volume
  • LEL is the next unit of measurement. It is a percentage of a compound’s explosive %(vol) level.
  • 100% LEL is the lowest concentration at which a flammable substance can produce a fire or explosion when ignited.
  • UEL (Upper Explosive Limit) is the maximum concentration of gas in air that will burn.
  • Each compound (gas) has a different LEL or the point at which the compound will burn or become explosive.
  • Most flammable compounds become explosive at less than 5%(vol).
  • Each gas has a different LEL and UEL.
  • %Gas is the highest unit of measurement, the amount of pure gas.

How Do Gas Detection Sensors Work?

Most gas detectors detect oxygen deficiency, toxic gases, and combustible gases. Many technologies are used in the industry.

How does an Oxygen Sensor work?

The Oxygen Sensor is an electrochemical sensor. A fuel-based electrochemical sensor can detect any gas that can be oxidized or reduced electrochemically. 

The consumption of oxygen produces a current (µA), which is linearly proportional to the gas concentration in the air. 

Since the oxygen sensor is constantly exposed to oxygen, the normal life of the sensor is between 1-2years.

How does the combustible sensor work?

A combustible sensor consists of two coils of fine platinum wire, each embedded in a bead of alumina and connected electrically in a bridge circuit. 

One of the beads is impregnated with a special catalyst, which promotes oxidation, and the other is treated to inhibit oxidation. 

Current is passed through the coils so that they reach a temperature at which gas oxidation readily occurs at the catalyzed bead (about 500°C). 

This raises the temperature further, increasing the resistance of the platinum coil in the catalyzed bead, leading to an imbalance of the bridge. 

For most gases, this output change is linear up to and beyond 100% LEL, and response time is only a few seconds to detect alarm levels (typically 20% LEL).

How does the Toxic sensor work?

The Toxic Sensors are also electrochemical sensors operating with the same basic principles as the oxygen sensor.

Electrochemical sensors consume minute amounts of gas, and the absorption of gas and electric output is controlled by a “diffusion barrier.”

Gas sensors maintenance

Bump Check

A bump test is a functional test of the gas monitor, which ensures that the sensors will respond to their target gas and that the alarms will function.

This is performed by briefly exposing the sensors to their target gas. Bump testing should be performed before each day’s use.

Bump tests check for sensor and alarm functionality but do not measure sensor accuracy and do not make adjustments to the instrument in the way that calibration does.

What Is A Bump Test In Gas Detection?

Calibration

They must be calibrated regularly to keep sensors operating at peak efficiency and accuracy.

Calibration is part of the regular maintenance process, and it ensures that the monitor is reading the correct level of gas.

Portable detectors are exposed to various environments and must be calibrated more frequently than standing sensors.

Proper sensor maintenance is crucial. A contaminated sensor can misread gas levels, resulting in hazardous results.

Gas Detector Calibration

Conclusion

That is the gas detection overview. This article covered the definition of gas detection, its necessity, and how some of the most common sensors work. Thank you for reading.

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