Plot Settings

Time horizon (s)

Time step (s)

HRR units

Y-axis scale

Heat release rate grows as Q̇ = αt². NFPA defines four standard growth rates by the time required to reach 1055 kW (1000 BTU/s): slow (600 s), medium (300 s), fast (150 s), and ultra-fast (75 s).

NFPA Standard Curves

Toggle which standard curves are plotted.

Slow — α = 0.00293 kW/s²

Medium — α = 0.01172 kW/s²

Fast — α = 0.04689 kW/s²

Ultra-fast — α = 0.1876 kW/s²

Custom Growth Curve (optional)

Plot a user-defined curve

Mode

α (kW/s²)

Use this for design fires whose growth doesn’t match a standard NFPA category — e.g., back-calculated from a fire test or specified by an authority having jurisdiction.

Peak HRR Cap (optional)

Cap curves at a peak HRR (steady-burning plateau)

Peak HRR

Cap units

When enabled, each curve grows as αt² until it reaches the peak, then holds at the peak through the time horizon. No decay phase.

Excel export includes a parameters sheet and an HRR vs. time sheet at the chosen time step, with one column per plotted curve. Suitable as input for FDS, CFAST, PyroSim, and NFPA 92 smoke-control design-fire tables.

Curve Summary

Curve	α (kW/s²)	t to 1 MW (s)	Q̇ at t_max

References: NFPA 72 Annex B (fire detection); NFPA 92 (smoke control); SFPE Handbook of Fire Protection Engineering, design fire curves.