Heat detectors offer an acceptable, but less sensitivealternative to smoke detectors if environmental conditions ruleout their use. 601H-R (rate of rise) and 601H-F (fixed temperature) detectorsdetect abnormally high rates of rise of temperature andabnormally high (static) temperatures respectively.For general use and particular where the ambient temperaturemay be low, a rate of rise heat detector 601H-R is to bepreferred. A fixed temperature limit is also incorporated inthese detectors. In many environments, e.g. kitchens, canteensand boiler rooms, sudden large changes in temperature areconsidered normal therefore rate-of-rise detectors are generallynot suitable in these cases and a slower response fixedtemperature detector 601H-F shouldbe used.