Design criteria by agent in clean-agent extinguishing systems and comparison (Temiz Gazlı Söndürme Sistemlerinde Söndürme Maddesi Seçimine Göre Değişen Tasarım Kriterleri ve Sistemlerin Karşılaştırılması)

Overview

The paper was presented at the 16th National Installation Engineering Congress (TESKON 2025, Izmir) and appears on p. 1362 of the proceedings; the author is Olcay Cömert and the publisher is the TMMOB Chamber of Mechanical Engineers. The text explains how fire class definitions, safety factors, discharge times, occupant-exposure limits (NOAEL/LOAEL) and altitude corrections differ between European and American rules.

Among halocarbon gases, GWP is 3350 for HFC-227ea and 1 for FK-5-1-12. NOAEL/LOAEL are 9% / 10.5% for HFC-227ea, 10% / over 10% for FK-5-1-12 and 43% / 52% for inert gases (about 12% / 10% O2 equivalent at sea level). Halocarbon systems must reach 95% of design concentration (including the 1.3 safety factor) within 10 s; inert systems within 60 s for class B and 120 s for class A and higher-hazard A.

Under NFPA 2001, inert gas below 43% is allowed with exposure limited to 5 min, 43-52% with exposure limited to 3 min, and 52-62% only in normally unoccupied rooms with exposure under 30 s. Inert systems reduce room oxygen to roughly 12-15% to stop combustion while remaining breathable. EN/ISO treat electrical fires within class A; higher-hazard conditions include cable bundles over 100 mm, trays filled over 20% and equipment energised above 5 kW during extinguishing.

Agent quantity is derived from net volume and a flooding factor, and altitude correction factors are required when ambient pressure differs from sea level by more than 11%. The paper also discusses the GWP and PFAS concerns that affect the future of chemical agents. The related sources are TS EN 15004-1, ISO 14520 and NFPA 2001.

Key points

1. GWP: HFC-227ea = 3350, FK-5-1-12 = 1.
2. NOAEL/LOAEL: HFC-227ea 9% / 10.5%; FK-5-1-12 10% / over 10%; inert gases 43% / 52% (about 12% / 10% O2 equivalent at sea level).
3. Inert gas below 43% allowed with exposure limited to 5 min; 43-52% with 3 min; 52-62% only in normally unoccupied rooms with exposure under 30 s (NFPA 2001).
4. Inert systems reduce room oxygen to roughly 12-15% to stop combustion while remaining breathable.
5. Halocarbon systems must reach 95% of design concentration (incl. 1.3 safety factor) within 10 s; inert systems within 60 s for class B and 120 s for class A/higher-hazard A.
6. EN/ISO treat electrical fires within class A; higher hazard: cable bundles over 100 mm, trays filled over 20%, equipment energised above 5 kW during extinguishing.
7. Altitude correction factors are required when ambient pressure differs from sea level by more than 11%.

Using it in design

• In the fire-suppression catalog, store agent type, GWP, NOAEL/LOAEL, design concentration, safety factor and discharge time per standard.
• Warn when design concentration exceeds NOAEL in an occupied room without delay/abort.
• Warn when a room is not marked for integrity (door fan) testing.
• Warn when site altitude requires a correction.

Who should read it

Mechanical and fire safety engineers designing gaseous suppression for data center and electrical rooms.

Related standards

• TS EN 15004-1
• ISO 14520
• NFPA 2001

Publication details

Authors

Olcay Cömert

Publisher

TMMOB Makina Mühendisleri Odası (MMO)

Year

2025

Document number

TESKON 2025 Bildiriler Kitabı, s. 1362

Event

16. Ulusal Tesisat Mühendisliği Kongresi (TESKON 2025), İzmir

Document language

English

Source type

Industry body

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation