Abstract: An apparatus and method for remotely detecting the presence of chemical ware nerve agents in a suspect thermal cloud. Infrared radiation emitted by a suspect thermal cloud is analyzed by means of a forward looking infrared thermal imager equipped with a spectral filter wheel having four passband filters; three of the spectral filter elements are spectrally optimized to respond to infrared radiation emissions characteristic of chemical warfare nerve agents. The variations in image contrasts of the thermograms generated by selectively filtering the infrared radiation emitted by the suspect thermal cloud are compared to determine the presence or absence of chemical warfare nerve agents in the suspect thermal cloud.

Abstract: A multiple-compressor refrigeration system for use in commercial refrigeration applications includes a plurality of compressors of unequal refrigeration capacity connected in a refrigeration circuit that includes a condenser and a plurality of associated evaporators and expansion devices in remotely located refrigerated enclosures. A system controller is connected to a pressure responsive transducer that measures the suction pressure of the system and compares the so-measured suction pressure to a desired suction pressure and selects one of a plurality of 2.sup.n available compressor operating states in accordance with the measured difference. The system advantageously increases overall system efficiency by providing increments or decrements of compressor capacity that are more precisely matched to system load changes as compared to prior multiple-compressor systems.