Heat release rate is the total amount of heat produced per unit mass of fuel consumed per unit time. It is also defined as the amount of heat released to the atmosphere from the convective-lift fire phase of a fire per unit time.
Source: National Wildfire Coordinating Group. 2012. Glossary of Wildland Fire Terminology. PMS 205. Accessed on 9 September 2013. Available at http://www.nwcg.gov