What are different types of gas measuring equipments used on ships ?

Limitations of explosimeters:

The explosimeter has been designed to detect the presence of flammable gases and vapours. The instrument will indicate in a general way whether or not the atmosphere is dangerous from a flammability point of view. It is important to realize that such information obtained from the instrument is appraised by a person skilled in the interpretation of the reading, bearing in mind the environment.

2. The oxygen analyser

 The oxygen analyser is an instrument that measures the oxygen content of an atmosphere to establish whether entry is possible, but it is also employed for inerted spaces which must be retained under 5% oxygen to affect a safe atmosphere within the tank.

The oxygen sensor will be either an electromagnetic heated filament or an electrochemical resistor cell. The instrument was designed to measure the oxygen content only and will not detect the presence of any other gases. Oxygen analysers are portable instruments which draw a sample of the atmosphere for testing through a sampling hose by means of a rubber aspirator bulb. The principle of operation is a self-generating electrolytic cell in which the electric current is directly proportional to the percentage oxygen in a salt solution connecting to the electrodes.

The electrodes are connected to a micro-ammeter, so that the current read by the meter can be calibrated to indicate directly the percentage oxygen of the sample.