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Gas Monitors

Last updated: July 12, 2021

What Does Gas Monitors Mean?

A gas monitor is a device that is used to monitor an area for the presence of harmful gases. They can be portable monitoring systems or fixed monitoring systems. The latter are connected to alarms that will sound if a harmful gas is detected. Portable gas monitors are also frequently connected to alarm systems.

Gas monitors are used to prevent harm from both toxic gas and combustible gas. They can also be used to detect when an environment becomes dangerously oxygen deficient.

The gas that the monitor is designed to detect is referred to as the “target gas.”

Safeopedia Explains Gas Monitors

No single type of gas monitor can detect every type of harmful gas; as such, there are multiple different types of detection systems available. The ideal system depends both on what gas (or gases) need to be detected, as well as on the nature of the environment that the monitor will be used in. The key variable used in gas detection systems is the type of sensor that is used; the type of sensor determines what gas(es) the system can detect, as well as the environments that it can be used in.

The four primary types of gas detection sensors are:

  • Electrochemical gas sensors
  • Catalytic bead sensors
  • Infrared gas sensors
  • Photoionization (PID) gas sensors

Galvanic and semiconductor sensors are also used in some instances. Electrochemical, catalytic bead and infrared sensors are the most commonly used sensors. While most gas detection systems are only used to detect a single type of gas, multi-gas detection systems are also available. These are used in environments in which there is the potential for multiple types of harmful gas to be present. Multi-gas systems may use multiple sensors to detect each type of gas, or may simply be calibrated to detect multiple gases across a single sensor.

The use of gas monitors is legally required in a variety of workplace settings that may feature harmful atmospheric conditions. This legal requirement exists in all jurisdictions that have advanced occupational health and safety regimes.

OSHA’s requirements for the use of harmful gas monitors are task-specific, and as such, cover a variety of different standards across general industry, construction and maritime industries. These standards also specifically require that the gas monitor be accurately calibrated; however, OSHA only provides advice — not legal requirements — on how to properly calibrate a monitor.

Proper calibration is vital to the effectiveness of a gas monitor. Not only does calibration ensure that the amount of gas in the environment is measured accurately, it is often necessary to ensure that the sensor can detect the gas at all: Electrochemical gas sensors detect gases by causing a small electrical reaction and then measuring that reaction to see if it matches the reaction that should be caused if the target gas is present. If the measurement is wrong, then this comparison will fail, and the presence of the gas will go undetected.

Although there is no single U.S. standard for the proper calibration of gas monitors, employers are still expected to ensure that proper calibration takes place. In the event that an accident or other reportable safety incident occurs, employers will be expected to show that their calibration requirements follow some sort of recognized system, such as the manufacturer’s guidelines that are provided with any gas monitor upon purchase.

There are numerous situations in which different types of sensors may be useful for the same detection task; however, each sensor has its own pros and cons, and it is important for employers to consider all of them before deciding which sensor to use.

For example, confined space work often requires the use of either a catalytic bead sensor or an infrared sensor in order to detect the presence of combustible gases. Catalytic bead sensors are capable of detecting a wider range of gases than IR sensors are; however, they may also be “poisoned” by exposure to certain gases that an IR sensor would have no problem withstanding. Thus, when selecting a gas monitor, the ideal choice will vary depending on the situation.

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