Example calculation table
| Case | Volume (m³) | Temp (°C) | Altitude (m) | Conc (%) | Adj. CO2 (kg) | Cyl (45 kg) |
|---|---|---|---|---|---|---|
| Electrical room | 144.00 | 20 | 0 | 34 | ~222.30 | 5 |
| Generator enclosure | 96.00 | 30 | 500 | 30 | 156.40 | 4 |
| Archive vault | 210.00 | 18 | 1200 | 40 | 420.10 | 10 |
Formula used
This calculator estimates CO2 required to reach a target volumetric concentration in a sealed space using an ideal-gas mixing approach. Ambient pressure is estimated from altitude, and density effects are handled via temperature.
- V = L × W × H (or manual volume input)
- P(alt) ≈ 101.325 × (1 − 2.25577×10⁻⁵·alt)^{5.25588} kPa
- n_air = (P·V) / (R·T)
- n_CO2 = (x / (1 − x)) · n_air, where x = concentration/100
- m_base = n_CO2 · M_CO2
- m_adj = m_base / η · (1 + leak) · (1 + safety)
- cylinders = ceil(m_adj / cylinder_capacity)
How to use this calculator
- Measure the internal room dimensions, or enter the net volume.
- Set temperature and altitude to match site conditions.
- Enter the design concentration specified by your fire strategy.
- Add leakage allowance and discharge efficiency for realistic losses.
- Apply a small safety factor if inputs are uncertain.
- Click Calculate, then download CSV or PDF for records.
Design Inputs That Drive Agent Mass
CO2 quantity depends first on the net flood volume. Use internal dimensions for a quick estimate, then refine with a net volume that removes duct voids, open shafts, or excluded zones. Temperature and altitude influence ambient pressure and gas density; warmer air or higher elevation typically increases the mass needed to reach the same volumetric concentration.
Interpreting Concentration Targets
The design concentration is a volumetric target for the final gas mixture. Select it from your fire strategy and equipment risk profile, and apply a consistent basis across similar rooms. Higher targets provide stronger suppression potential but increase stored agent mass, venting demand, and safety controls. Always align concentration with warning systems, access control, and evacuation procedures.
Allowances for Leakage and Discharge Losses
Real spaces are not perfectly sealed. The leakage allowance accounts for gaps, doors, cable penetrations, and construction tolerances. Discharge efficiency represents practical losses from piping, nozzle distribution, stratification, and imperfect mixing. A conservative efficiency and leakage factor reduces the risk of under-delivery during commissioning and supports more reliable acceptance results.
Cylinder Planning and Site Logistics
After calculating adjusted mass, cylinder count translates the design into procurement and installation needs. Compare the computed mass to cylinder capacity (net agent) and round to a usable ordering increment. Consider storage footprint, handling routes, and restraint details. Provide spare capacity if future envelope changes are likely, and coordinate clear labeling for maintenance turnover.
Documentation and Review Checks
Record inputs, assumptions, and factors used so reviewers can verify decisions. Validate dimensions against as-built drawings, confirm altitude and typical operating temperature, and review openings that could reduce hold time. Use the CSV and PDF exports to support design reviews, cost estimates, and site commissioning checklists.
1) What volume should I use for irregular rooms?
Break the room into simple blocks, sum their volumes, or enter a net volume. Exclude large open shafts if they are not intended to be flooded.
2) Why does altitude matter in the calculation?
Higher altitude generally means lower ambient pressure. To achieve the same target concentration by volume, more moles of CO2 are needed, which increases required mass.
3) How do I choose a discharge efficiency value?
Use supplier guidance or past commissioning data for similar piping and nozzle layouts. If unknown, choose a conservative value to reduce under-delivery risk.
4) What does leakage allowance represent?
It covers expected losses through doors, penetrations, imperfect seals, and construction tolerances. Higher leakage factors increase required CO2 mass to maintain the target mixture.
5) Does this calculator replace code compliance checks?
No. It provides a planning estimate. Final designs should be reviewed against applicable standards, hazard analysis, and system commissioning requirements.
6) Can I use the PDF and CSV for submittals?
Yes for supporting documentation, estimates, and review notes. Include your project reference, assumptions, and verification steps, and keep vendor calculations alongside these exports.