Abstract: Apparatus is provided which permits highly accurate remote measurement of methane gas concentrations even in daylight through the use of an extremely narrow spectral filter centered on the Q-branch of the methane absorption band at 3.3 microns and through the use of cooperating comparison channels with digital processing for real time correction of data to compensate for surface temperature, atmospheric temperature and atmospheric water absorption factors.

Abstract: A regenerative room air exchanger for use in a house has a first vertically disposed conduit through which room air flows to be exhausted, the first conduit including a first set of vertically disposed channels, a second vertically disposed conduit through which fresh air flows to the room, the second conduit including a second set of vertically disposed channels with the first and second sets of channels being interdigitated and in counterflow heat exchange relationship with each other, and a jacket surrounding and spaced from the interdigitated channels to form a third vertically disposed conduit between the jacket and the channels, the third conduit being in fluid communication with the first conduit. An exhaust blower is in fluid communication with the first conduit and an inlet blower is in fluid communication with the second conduit.