Is a CO2 system safe for occupied areas?

No, CO2 is lethal at the concentrations used for fire suppression. For areas that may be occupied, strict safety measures like time delays, audible and visual alarms, and evacuation procedures are mandatory as per Clause 6.

What is the minimum design concentration for a server room or data center?

For under-floor or in-cabinet protection, 50% is specified. For total flooding of the entire room (as an electrical hazard), a minimum of 34% is a starting point, but the specific hazard type and volume must be assessed per Annex A.

What is a 'soak time' and why is it important?

Soak time is the duration for which the design concentration must be maintained after discharge to extinguish deep-seated, smoldering fires (e.g., in paper archives). Clause D.3 requires a minimum 20-minute soak time for such hazards.

How is the required quantity of CO2 calculated?

For total flooding, it is calculated based on the net volume of the enclosure and the required design concentration, using the flooding factors in Table A.2 or the formula in Annex C.

IS 15528

: 2004

Gaseous Fire Extinguishing Systems - Carbon Dioxide Total Flooding and Local Application ( Sub-Floor and In-Cabinet), High and Low Pressure (Refrigerated) Systems

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This standard specifies requirements for the design, installation, testing, inspection, and maintenance of carbon dioxide (CO2) fire extinguishing systems. It covers total flooding systems for enclosures and local application systems for specific equipment, addressing both high-pressure cylinders and low-pressure refrigerated storage.

Gaseous Fire Extinguishing Systems - Carbon Dioxide Total Flooding and Local Application ( Sub-Floor and In-Cabinet), High and Low Pressure (Refrigerated) Systems

Quick Reference Values

Minimum design concentration for electrical hazards34%

Minimum design concentration for cable tunnels/vaults65%

Maximum discharge time for surface fires (total flooding)60 seconds

Minimum soaking time for deep-seated fires20 minutes

Maximum oxygen level for safe re-entry19.5%

Typical pre-discharge alarm time delay20 to 30 seconds

Key Formulas

W = (V/S) * [ C / (100 - C) ] — Mass of CO2 for total flooding based on concentration

Q = 2 * A * q — Flow rate for local application systems where A is area and q is the application rate

Practical Notes

CO2 is an asphyxiant at design concentrations and is lethal. Personnel safety features like pre-discharge alarms, time delays, and maintenance lock-out switches are critical and must be strictly implemented and tested.

The effectiveness of a total flooding system depends on the room's ability to hold the gas concentration. A Room Integrity Test (Door Fan Test) as detailed in Annex F is mandatory during commissioning and periodic maintenance.

This standard is heavily influenced by NFPA 12 (Standard on Carbon Dioxide Extinguishing Systems), which can be a valuable reference for additional design guidance and context.