**Keith Dear**

School of Public Health, The University of Adelaide, Adelaide SA 5005, Australia; keith.dear@adelaide.edu.au; Tel.: +61-403-475-160

Received: 29 May 2018; Accepted: 18 July 2018; Published: 22 July 2018

**Abstract:** Workers exposed to high ambient temperatures, either indoors or out, work slower. The few studies that have measured this loss of productivity show a degree of consistency across widely varying settings. I develop a class of 5-parameter probability models that express productivity as a function of environmental heat and show how the method of fitting can be adapted according to the completeness of the data available. As well as modelling the mean output, it is important to also consider variation between workers, and the model presented here achieves this. The method is illustrated using three previously published datasets from different industries and work environments.

**Keywords:** workplace; heat stress; productivity loss; beta distribution
