This nonautomatic detector, or portable air analysis apparatus, can be used underground, or samples of air can be brought out of the mine in small rubber bladders and analyzed at the surface. This apparatus depends for its action on the fact that when methane is burned in air (oxygen) a definite chemical action takes place. When the resulting steam condenses to water there is a reduction in pressure and in the McLuckie detector this reduction of pressure, which is proportionate to the methane present, is indicated by the height of the liquid in one limb of the U-tube which rises up the side of the scale: the scale is graduated from 0% to 3% in steps of 0.1%.