A crude model for estimating the evaporation heat loss due to a sprinkler water spray in a smoke layer is reported. It is found that the evaporation heat loss lies below 11.2% of the convective loss when water travels through a hot gas layer 0.9 m thick and 60 C under normal sprinkler operating conditions. It is also found that the value may go up to 26% if the smoke layer reaches 1.5 m and 273 C.