While carbon dioxide is used in some extinguishers as an inert propellant the gas is also used extensively as a blanketing agent. In a carbon dioxide portable extinguisher, the carbon dioxide is in liquid form and is at a pressure of 6 bar at 20℃, necessitating a far stronger container. This type of extinguisher can only be recharged ashore. To check for leakage a record should be kept of the weight of the extinguisher, Alternatively the liquid level can be determined by using a special instrument which uses a radioactive source and a Geiger-Muller counter to detect the gas/liquid interface although this method is usually only used on large fixed CO2 installation.This could be lethal if discharged accidentally in a confined space and for this reason this type of extinguisher in not allowed in the accommodation.