When it comes to gas monitoring, accuracy is open to each manufacturer’s interpretation. Officially, accuracy is a statement expressed as a percentage of the closeness of the reading on the gas monitor to the actual concentration; many manufacturers use this as an umbrella term representative of much more, including resolution and sensitivity. To acquire the most comprehensive insight into how the device will perform when used on your work site, it is important to review the following separately.
- Accuracy: Typically listed with a plus or minus 5 percent, it is associated with a confidence interval of 95 percent. This means in 95 out of 100 results; the readings should be within plus or minus 5 percent of the actual gas concentration. It is important to understand the device’s measuring range to determine whether the reading could be close to an actual concentration or completely off the mark. There are many factors involved in obtaining accurate gas detection measurements, and they extend well beyond the instrument itself. Calibration standards, calibration methods, ambient conditions, chemisorption, entrained water and particulate, and interferences can all play a part in destroying accuracy.
- Resolution: This refers to the reading on the display of the monitor. Typically, sensors should have a resolution finer than the accepted occupational exposure limit for the target gas.
- Sensitivity: Indicates the lowest detectable reading that can be reliably measured and displayed. It is an absolute quantity of the gas that can be detected.
By reviewing each of these individual metrics, you will be in a stronger position to select a gas monitor that will help you optimise on-site safety.
Also useful in further establishing that an instrument will reliably perform within your worksite is the examination of ambient conditions. Ambient conditions typically refer to the operational specifications, in particular temperature, pressure and relative humidity. These are designated by each manufacturer depending on specifications for the unit.
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