Replacement rate of filament lamps in an organisation: A rule of thumb

Abstract

We address the issue of renewal rate of fused filament lamps in an organisation and modify the description given in an old edition of the IESNA Lighting Handbook (1968). This is achieved by applying the standard mortality curve to formulate an exact algebraic relation for the renewal fraction at successive stages. Finally, for the benefit of illuminating engineers a rule of thumb is developed, which estimates the saturation number of lamps to be replaced as a function of burning time, half-life and the total number of lamps installed.