Fire Load Density Calculator
ANA›Life Services Authority›National Calculator Authority›Fire Load Density Calculator
.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }
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
Floor Area Af (m²)
### Combustible Materials
Enter each material's mass and net calorific value. Add up to 10 materials.
Material 1
Mass mi (kg)
Net Calorific Value Hu,i (MJ/kg)
Combustion Factor ψi (0–1)
- Add Material
### Optional: Protected vs Unprotected
% of Fire Load in Protected Enclosures
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)
Occupancy Type (for reference)
-- Select for reference -- Offices: 80–200 MJ/m² (use 200) Offices (upper): 200 MJ/m² Dwellings: 300 MJ/m² Hospitals: 400 MJ/m² Libraries: 600 MJ/m² Industrial (general): 1000 MJ/m² Industrial (heavy): 1500 MJ/m²
Calculate Fire Load Density
#### 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.
- This calculator does not account for active fire suppression (sprinklers) or ventilation conditions, which are addressed separately in fire engineering assessments.
.fir-material-row { border: 1px solid #dde3ec; border-radius: 6px; padding: 10px 14px; margin-bottom: 12px; background: #f8fafc; } .fir-mat-label { font-weight: 600; color: #2c3e50; display: block; margin-bottom: 6px; } .fir-add-btn { background: #27ae60; color: white; border: none; padding: 7px 16px; border-radius: 5px; cursor: pointer; font-size: 0.9em; margin-top: 4px; } .fir-add-btn:hover { background: #219a52; } .fir-remove-btn { background: #e74c3c; color: white; border: none; padding: 4px 10px; border-radius: 4px; cursor: pointer; font-size: 0.82em; margin-top: 6px; } .fir-remove-btn:hover { background: #c0392b; } .fir-risk-low { color: #27ae60; font-weight: 700; } .fir-risk-medium { color: #f39c12; font-weight: 700; } .fir-risk-high { color: #e67e22; font-weight: 700; } .fir-risk-vhigh { color: #e74c3c; font-weight: 700; } .fir-table { width:100%; border-collapse:collapse; margin-top:10px; font-size:0.9em; } .fir-table th { background:#2c3e50; color:white; padding:6px 10px; text-align:left; } .fir-table td { padding:5px 10px; border-bottom:1px solid #eee; } .fir-table tr:nth-child(even) td { background:#f5f7fa; }
(function(){ var firMatCount = 1; var firMaxMats = 10;
window.firAddMaterial = function() { if (firMatCount >= firMaxMats) { alert("Maximum 10 materials allowed."); return; } firMatCount++; var n = firMatCount; var container = document.getElementById("fir-materials-container"); var div = document.createElement("div"); div.className = "fir-material-row"; div.id = "fir-mat-row-" + n; div.innerHTML = 'Material ' + n + '' + 'Mass mi (kg)' + '' + 'Net Calorific Value Hu,i (MJ/kg)' + '' + 'Combustion Factor ψi (0–1)' + '' + 'Remove'; container.appendChild(div); };
window.firRemoveMaterial = function(n) { var row = document.getElementById("fir-mat-row-" + n); if (row) row.remove(); };
function firGetVal(id) { var el = document.getElementById(id); if (!el) return null; var v = parseFloat(el.value); return isNaN(v) ? null : v; }
function firRiskLevel(qf) { if (qf ⚠ Please enter a valid floor area greater than 0.'; return; }
// Protected percentage var protPct = firGetVal("fir-protected-pct"); if (protPct === null) protPct = 0; if (protPct 100) { resultDiv.innerHTML = '⚠ Protected enclosure percentage must be between 0 and 100.'; return; }
// Gather materials var totalQ = 0; var matRows = []; var anyMaterial = false; var errors = [];
for (var n = 1; n 1) { errors.push("Material " + n + ": combustion factor must be between 0 and 1."); continue; }
var Qi = m * hu * psi; totalQ += Qi; matRows.push({ n: n, m: m, hu: hu, psi: psi, Qi: Qi }); anyMaterial = true; }
if (errors.length > 0) { resultDiv.innerHTML = '⚠ ' + errors.join("⚠ ") + ''; return; }
if (!anyMaterial) { resultDiv.innerHTML = '⚠ Please enter at least one material with mass and calorific value.'; return; }
// Calculations var qf = totalQ / Af; // MJ/m² var qfEff = qf * (1 - protPct / 100); // effective after protection var risk = firRiskLevel(qfEff);
// Reference comparison var refEl = document.getElementById("fir-occupancy"); var refVal = refEl ? parseFloat(refEl.value) : NaN; var refLabel = refEl ? refEl.options[refEl.selectedIndex].text : ""; var refHtml = ""; if (!isNaN(refVal) && refVal > 0) { var ratio = qfEff / refVal; var ratioColor = ratio Reference Design Value (EN 1991-1-2)' + refVal.toFixed(0) + ' MJ/m²' + 'Ratio qf,eff / Reference' + ratio.toFixed(2) + (ratio '; }
// Material breakdown table var matTableRows = ""; for (var i = 0; i Material ' + r.n + '' + '' + r.m.toFixed(2) + '' + '' + r.hu.toFixed(2) + '' + '' + r.psi.toFixed(2) + '' + '' + r.Qi.toFixed(1) + ''; }
resultDiv.innerHTML = '### Results ' +
'' + 'ParameterValue' + 'Floor Area Af' + Af.toFixed(2) + ' m²' + 'Total Fire Load Qfi' + totalQ.toFixed(1) + ' MJ' + 'Fire Load Density qf' + qf.toFixed(1) + ' MJ/m²' + 'Protected Enclosure Reduction' + protPct.toFixed(0) + '%' + 'Effective Fire Load Density qf,eff' + '' + qfEff.toFixed(1) + ' MJ/m²' + 'Risk Classification' + risk.label + '' + refHtml + '' +
'#### Material Breakdown ' + '' + 'MaterialMass (kg)Hu (MJ/kg)ψQi (MJ)' + matTableRows + 'Total' + totalQ.toFixed(1) + ' MJ' + '' +
'' + 'Interpretation: An effective fire load density of ' + qfEff.toFixed(1) + ' MJ/m² ' + 'is classified as ' + risk.label + '. ' + 'Values below 200 MJ/m² are generally low risk; 200–400 MJ/m² medium; 400–800 MJ/m² high; above 800 MJ/m² very high. ' + 'Compare against EN 1991-1-2 Table E.4 design values for your occupancy type.' + ''; }; })();
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