Foam Fire Extinguishing Calculations & Free Excel Tool

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Foam Fire Extinguishing Calculations: Designing fire supresion system with foam is technique. Which is used to stop fire from spreading. they calculates volume of foam and how much concentrate to put in it and how fast it should come out. if you want protect warehouse from fire you use high expansion foam system. and if you want protect from liquid fire. You use low expansion foam. you got know formulas and standards to make sure fire stops and its legal.

Types of Firefighting Foam & Application Rates

1. Low-Expansion Foam
   Low-expansion foam has an expansion ratio up to 20:1 and is ideal for Class B hydrocarbon fires. Recommended application rates are 0.10–0.30 L/min·m² so it covers fuel surfaces effectively.Medium-Expansion Foam
   Medium-expansion foam expands 20:1 to 200:1 and suits enclosed spaces. It’s used for spill control at typical rates of 0.10–0.15 L/min·m² because it balances coverage and discharge volume.High-Expansion Foam
   High-expansion foam expands 200:1 to 1000:1 and is perfect for large compartments like aircraft hangars. Use it based on compartment volume and desired foam curtain height.

Core Calculation Steps

1. Determine Protected Area or Volume
   – For surface fires, measure the pool area in square meters (m²).
   – In enclosed spaces, calculate room volume (m³) for high-expansion systems.
2. Select Concentrate Percentage
   – Typical foam concentrates range from 1 % to 6 % by volume.
   – Choose per manufacturer data and fuel type.
3. Compute Foam Solution Flow Rate (Qₛ)Qs=A×RQ_s = A \times R– Qₛ: solution flow (L/min)
   – A: protected area (m²)
   – R: application rate (L/min·m²)
4. Calculate Water & Concentrate VolumesVwater=Qs1+C×t,Vconc=Qs−VwaterV_{water} = \frac{Q_s}{1 + C}\times t \quad,\quad V_{conc} = Q_s – V_{water}– C: concentrate fraction (e.g., 0.03 for 3 %)
   – t: required discharge duration (minutes)
5. Verify Discharge Duration & Storage
   – Ensure stored concentrate and water meet the duration (usually 15–30 min).
   – Add safety margin (10–20 %) for pump inefficiencies and nozzle losses.

Example Calculation

• Protected Area: 100 m²
• Application Rate (R): 0.20 L/min·m²
• Concentrate Percentage (C): 3 % (0.03)
• Duration (t): 20 min

1. Qₛ: 100 m² × 0.20 L/min·m² = 20 L/min
2. Water Volume: (20 L/min ÷ 1.03) × 20 min ≈ 388.35 L
3. Concentrate: 20 L/min − (388.35 L ÷ 20 min ≈ 19.42 L/min) = 0.58 L/min
   – Total concentrate ≈ 0.58 L/min × 20 min = 11.63 L

Foam Fire Extinguishing Calculations: How to Use

Our Foam Fire Extinguishing Calculator automates these steps. First, download and open the Excel file and enable editing. Then enter the protected area, application rate, concentrate percentage, and duration because accurate inputs drive precise results. You will instantly see the solution flow, water volume, and concentrate volume. Finally, adjust the parameters to test different rates. Or durations so you can refine your system sizing.