Methanometer

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 belt with other tools.

It is highly explosive and had previously been detected by the blue halo effect it gave to the flame of a safety lamp.

[1] These relied on such methods as the differential heating of an incandescent platinum filament, or by measuring the higher absorption of infrared radiation by gas containing methane.

When exposed to methane-contaminated air, the coated filaments heat up due to oxidation of the methane, and the resulting imbalance in the resistance of active and inactive elements can be displayed on a calibrated meter.