t² (t-squared) Fire Calculator

This calculator can be used to determine the heat release rate of a t² fire (also known as a t-squared fire) at a specific time.

Q = Qg (t/tg

Q = Total Heat Release Rate (kW)
Qg = Reference Heat Release Rate (kW)
t = Time from Effective Ignition Time (s)
tg = Characteristic Time of Growth (s)

NFPA Standard 204 categorises t² fires into four categories based on the amount of time taken to reach 1055 kW.

Ultra-fast 75 seconds
Fast 150 seconds
Medium 300 seconds
Slow 600 seconds