The problem of false alarms is defined showing the demanding nature of the application. Detector dependencies are discussed relative to reliability, such as: pyroelectric material, possible depolarization, long term stability, use of separate load resistors to achieve predictable time constants, response to temperature changes, soft error rate, potential microphonics, and the need for EMI protection. Highest reliability of the circuit design involves consideration of the internal FET of the detector as well as careful selection of coupling capacitors, resistors and the power supply. The detector signal's dependence on optical design is identified and the relationship of signal-to-noise specified. User handling precautions of the detector are also given. Appendices show 1) the relationship of S/N ratio to false alarm rate in Gaussian terms, 2) failure rates of alarm components, 3) evaluation of approaches to testing, and 4) a brief discussion of soft error mechanisms.