A cycle comprises a primary crank arranged for rotation about a first axis, a secondary crank, and connection means for selective connection of the secondary crank to the primary crank at a selected one of a plurality of positions on both the primary crank and the secondary crank. Electromagnetic radiation, such as infrared light, is directed from the monitored volumes onto at least two sets of detector elements having separate outputs on a pyroelectric substrate of an infrared detector. , carbon dioxide, from a gaseous mixture using a hollow fiber membrane module. 1\u02dc12 MPa, and the operating temperature thereof is 1350\xb0 C.