Not calibrating is the first in a series of Seven Deadly Sins tutorials by gas-detection specialist, Crowcon. By highlighting the most common causes and effects of each ”sin”, Crowcon will provide managers and employees with a greater awareness of what we believe are the Seven Deadly Sins of gas detection, how to avoid them and save lives.
‘It was OK last time’
Complacency is a major cause of not calibrating gas-detection equipment. The safety provided by an apparently functional gas detector can lead to the complacent assumption that there is little or no risk. The problem, however, is that, for the assurance of safety, a gas detector has to be monitoring accurately.
Extremes and exposure
Factors which can compromise the performance and accuracy of a gas detector include: adverse working conditions; extremes of temperature or humidity; exposure to contaminants such as silicone or solvents and exposure to high concentrations of gas; mechanical shock or stress. Any of these factors can lead to a gas detector displaying an inaccurate reading, and this can mean that the detector may not sound an alarm even in the presence of toxic or flammable levels of gas.
The Crowcon calibration checklist
Keeping things simple, there are three steps to calibrating a gas detector to check and reset the detector’s response to a target gas:
Step 1: Zero the detector in fresh air (and be sure it is fresh!) or synthetic air
Step 2: Expose the detector to a known concentration of the target gas
Step 3: Adjust the detector until it shows the correct level of gas
The Expert dimension
For some gases, such as flammable gases and VOCs, an alternative method of calibrating detectors may be required. Here, calibration can be carried out using a different, related gas and a cross- calibration factor is applied to determine the accuracy of the detector.
Calibration should leave nothing to chance. In addition to following the recommendations of the detector’s manufacturer, an expert will take into account flow paths and flow rates, pressure, temperature, humidity, cross sensitivities, the time required for the sensors to respond and the expulsion of the waste gas.
Calibrating to save lives
There are many factors which can compromise the accuracy of detectors and, therefore, compromise the lives of the people using them. These factors make it essential for operators to understand that scheduled calibration is a lifesaver. It is also essential for managers to take a rigorous approach to ensuring that calibration is performed on-time and using the correct calibration test.
Sin #2: Not bump testing