Portable Gas Detector Bump-Testing vs Calibration

How Often Do We Need to Bump Test & Calibrate Portable Gas Detectors

Bump (or Span) Check

A bump check is a means of verifying calibration by exposing the instrument to a known concentration of test gas. The instrument reading is then compared to the actual quantity of gas present (as indicated on the cylinder). if the instrument’s response is within an acceptable range of the actual concentration, then its calibration is verified. When performing a bump test, the test gas concentration should be high enough to trigger the instrument alarm. if the bump test results are not within the acceptable range, then a full calibration must be performed.

Instrument Calibration

Whether an instrument warns and / or alarms at the proper time depends on its ability to translate the quantity of gas it detects into an accurate reading. “calibration” refers to an instrument’s measurement accuracy relative to a known concentration of gas. Gas detectors perform relative measurements: rather than independently assessing the quantity of gas present, they measure the concentration of the air sample and then compare it to the known concentration of the gas that the instrument is configured to sample. This “known concentration” serves as the instrument’s measurement scale, or reference point.

Full Calibration

A full calibration is the adjustment of the instrument’s reading to coincide with known concentrations (generally a certified standard) of zero and span gases, to compensate for calibration drift. In most cases, a full calibration is only necessary when an instrument does not pass the bump test (or after it has been serviced).

The Million Dollar Question – Frequency of Calibration

The frequency of calibration depends on the sensor’s operating time, conditions of use (including chemical exposure) and user experience with the instrument. New sensors should be calibrated more often until the calibration records prove sensor stability. The calibration frequency can then be reduced to the schedule set by the safety officer or plant manager.

Bump Test
BW-Ultra-Multi-Gas Detector

What are the regulations in Australia & NZ

Portable Gas Detectors require bump testing daily or Prior to Use, and if the detector fails the bump test then needs to be re-calibration. The manufacturers recommendations as published in their Instruction Manuals should be followed for calibration intervals.

What are do calibration Intervals Recommended by the Manufacturers

Portable Gas Detectors however require bump testing daily or Prior to Use, and if the detector fails the bump test, requires re-calibration. Most manufacturers do recommend re-calibration at least every six months or 180 days.

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