Abstract: An improvement upon cylindrical MIR element cells of the type that have a single seal at the openings of the cell body through which the cylindrical MIR element extends. The improvement is: (1) to position an additional seal between each such opening and the cylindrical MIR element so that there is a sealed space between the second seal and the original seal at each such opening; and (2) to position at least two passageways through the body of the cell, each such passageway in fluid communication with each of the above formed sealed spaces so that any leakage of a sample past the original seal is vented from the cell via one of the passageways. In a highly preferred embodiment of the present invention the portion of the cell body surrounding each such opening is made demountable and is provided with additional passageways and seals so that a purge fluid can be flowed through the passageways to a flow through detector to detect any leakage of a fluid sample past one of the original seals.