Fire Load Density Calculator
Calculate the fire load density (qf) of a compartment by summing the energy content of all combustible materials divided by the floor area. Used in fire safety engineering per EN 1991-1-2.
Compartment Floor Area
Combustible Materials
Enter each material's mass and net calorific value. Add up to 10 materials.
Material 1
Optional: Protected vs Unprotected
Protected enclosures (e.g. fire-rated cabinets) reduce the effective fire load. Enter 0 if none.
Reference Values (EN 1991-1-2 Table E.4)
Formula
Fire Load Density:
qf = Σ(mi · Hu,i · ψi) / Af
Where:
- qf = Fire load density (MJ/m²)
- mi = Mass of combustible material i (kg)
- Hu,i = Net calorific (lower heating) value of material i (MJ/kg)
- ψi = Combustion factor for material i (0 to 1); accounts for incomplete combustion
- Af = Floor area of the compartment (m²)
Effective fire load (accounting for protected enclosures):
qf,eff = qf · (1 − p/100)
Where p = percentage of fire load in protected enclosures.
Total Fire Load:
Qfi = Σ(mi · Hu,i · ψi) [MJ]
Assumptions & References
- Based on EN 1991-1-2:2002 (Eurocode 1: Actions on structures – Part 1-2: General actions – Actions on structures exposed to fire), Annex E.
- The net calorific value Hu (lower heating value) is used, not the gross calorific value. Typical values: wood ~17.5 MJ/kg, paper ~17 MJ/kg, plastics ~30–40 MJ/kg, textiles ~20 MJ/kg, rubber ~30 MJ/kg.
- The combustion factor ψ accounts for incomplete combustion. EN 1991-1-2 recommends ψ = 0.8 for cellulosic materials and ψ = 1.0 for liquid fuels. A conservative default of 1.0 may be used.
- Fire load density is referenced to the floor area (qf). It can also be referenced to the total enclosure surface area (qt), but floor-area reference is most common in design.
- Protected enclosures (fire-rated storage cabinets, vaults) may reduce the effective fire load per SFPE Handbook guidance.
- Design fire load densities from EN 1991-1-2 Table E.4 are 80th-percentile values for occupancy types and should be compared against calculated values.
- This calculator does not account for active fire suppression (sprinklers) or ventilation conditions, which are addressed separately in fire engineering assessments.
- For regulatory compliance, always verify with the applicable national annex and a qualified fire engineer.