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Vessels shipping coal should at all times carry on board instruments for measuring methane, oxygen and carbon monoxide gas concentrations, so that the atmosphere within the cargo space can be monitored. The instrument should be regularly serviced and calibrated so that it can provide the crewmembers with reliable data about the atmosphere within the cargo space. Care needs to be exercised in interpreting methane measurements carried out in the low oxygen concentrations often found in unventilated cargo holds. The catalytic sensors normally used to detect methane rely on the presence of sufficient oxygen for accurate measurement. This phenomenon does not affect the measurement of carbon monoxide or measurement of methane by infrared sensor. However, additional guidance should be sought from the manufacturer of the instrument.
An instrument required for measuring methane, oxygen and carbon monoxide concentrations should be fitted with an aspirator, flexible connection and a length of tubing, thus enabling a representative sample to be obtained from within the square of the hatch.
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