Abstract: A method and apparatus for determining the proportion of a paramagnetic gas in a mixture of gases is disclosed. There is provided an element which is able to oscillate in a magnetic field. A force acting on the element due to the presence of paramagnetic gas in the magnetic field changes according to the concentration of paramagnetic gas present. This change in force affects parameters of the oscillation such as damping and frequency, which may be monitored thereby to determine the concentration of paramagnetic gas present.

Abstract: A miniature source of modulated infra-red energy comprises a very thin heated wire strip (11) of low mass, mounted in a tensioned state by means of two resilient members (18), and a reflector (15) positioned behind the wire (11) so as to enhance the radiated energy. The source is hermetically sealed in an inert atmosphere with a cap (20). The cap (20) has an aperture (16) through which the energy emerges, this is sealed either with a window or a filter (17) if a specific wavelength is desired.

Abstract: A gas testing apparatus comprising a body (13, 14) defining a chamber (7), means (2, 3) for creating a magnetic field within the chamber in a first direction, a test body (20), means (19) for mounting the test body (20) for rotation about an axis parallel to the direction of the magnetic field, and gas inlet (9) and outlet (10) means for allowing gas flow through the chamber (7), characterised in that the gas inlet means (9) are arranged and disposed to supply gas to the chamber from two positions at opposite sides of the chamber whereby gas flow from each of the two positions will be parallel to the direction of the magnetic field but in opposition in order to minimize errors resulting from gas flow upon the test body. The chamber is of small volume i.e. less than 0.6 ml which enables the apparatus to be used for preliminary monitoring.