1) Measuring instrument 
A methanometer is an instrument used to measure methane gas in the air of a mine. The Mine Safety Appliances Company Ltd. manufactured the first type - W8 Methanometer around 1950 and it was approved for use by the Ventilation Regulations of 1947. The Methanometer could be powered by an Edison battery cap lamp and it could be carried on a miner`s....
instrument for detecting presence of methane
• (n.) An instrument, resembling a eudiometer, to detect the presence and amount of methane, as in coal mines.
Meth`a·nom'e·ter noun [ Methane + -meter .] An instrument, resembling a eudiometer, to detect the presence and amount of methane, as in coal mines. 
methanometer An instrument for measuring the concentration of methane in air; especially, in mines.