(a) Fire detecting devices of the fixed temperature type shall operate when the temperature rises to 165 degrees Fahrenheit, when installed in areas where the maximum temperature at the ceiling is 100 degrees Fahrenheit. Where higher temperatures normally exist at the ceiling, such as in furnaces or boiler rooms, kitchens, laundries, etc., fire detecting devices may operate at higher temperatures providing such higher operating temperatures are commensurate with the ceiling temperatures.

(b) Fire detecting devices of the rate-of-rise type shall operate whenever the rate of the rise in temperature exceeds 20 degrees per minute.