A thermally insulative label is provided. While fingers work better than the traditional stick-type toothbrush in maneuvering around inside the mouth, the lack of vibratingrotating in the bristle portion greatly diminished the flexibility of human fingers. Each output beamlet is split into a sensing beamlet and an associated reference beamlet. A gas sample from these separated gases can be mixed with a carrier gas and are conveyed to gas analyzing means where the concentration of the different hydrocarbon components of the gases in the mud can be continuously measured.