The degree of frost protection afforded by various concentrations of heaters of a simple design distributed over an area of 1 ac was investigated for a plantation of pineapples in southern Queensland. The area over which a temperature rise of a given amount was produced was found to increase linearly with the strength of the temperature inversion. The area also appeared to increase linearly with concentration of heaters over the range 53-188 per acre. This latter concentration produced a temperature rise of at least 30°F over about 1 ac, and at least 1°F over 2-1/4 ac. Tests with a combination of these heaters and a wind machine suggested that the areas of various temperature rises were equal to the sum of the areas produced by the two methods used separately.