Abstract: The source (12) has a heater element (122) sandwiched between elongate emitter plates (124 and 126). In operation, the source (12) is operated at temperatures in excess of 900.degree. C. and, preferably, at least about 1200.degree. C. to provide radiation in the 7-10 micrometer wavelength range. In one embodiment, the source (12) is used in conjunction with an elongate detector array (14) in a gas analyzer (10) for analyzing respiratory and anesthetic gases. Spherical mirrors (36a, 36b) and flat mirrors (38a, 38b) are employed to image the source (12) on the detector array (14). A linear variable filter (26) allows for analysis of the radiation at multiple wavelengths using detector array (14).