A Review of Design Values Adopted for Heat Release Rate Per Unit Area

When conducting fire and smoke modelling it is important to adopt an appropriate design fire. Calculations may adopt a design fire that is represented in terms of a heat release rate per unit area (HRRPUA). This paper provides a historical review of recommended values that are predominantly used in the UK as well as values from other jurisdictions where appropriate. It has been determined that many of the HRRPUA values provided in UK guidance are derived from ten fire incidents for industrial fires in the 1960s and 1970s, and five wood crib experiments undertaken in the 1960s. The HRRPUA values originally calculated from these incidents and experiments ranged from 86 kW/m2 to 650 kW/m2. The data was gradually adapted in various forms to consider shops and retail buildings, offices, hotel rooms and residential buildings, where variations in recommended values have occurred over time due to adjustments and calculations from various authors. In light of the observations, this paper provides updated recommended values from literature which relate to specific occupancies and building types. These are summarised as a range of potential values, such as 270 kW/m2 to 1200 kW/m2 for shops and 150 kW/m2 to 650 kW/m2 for offices, where designers will need to take care in considering the relevant source material.