ISO 14520-8:2016

INTERNATIONAL ISO
STANDARD 14520-8
Third edition
2016-10-01
Gaseous fire-extinguishing systems —
Physical properties and system
design —
Part 8:
HFC 125 extinguishant
Systèmes d’extinction d’incendie utilisant des agents gazeux —
Propriétés physiques et conception des systèmes —
Partie 8: Agent extincteur HCFC 125
Reference number
©
ISO 2016
© ISO 2016, Published in Switzerland
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ii © ISO 2016 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Characteristics and uses . 1
4.1 General . 1
4.2 Use of HFC 125 systems . 2
5 Safety of personnel . 5
6 System design . 6
6.1 Fill density. 6
6.2 Superpressurization . 7
6.3 Extinguishant quantity . 7
7 Environmental properties . 8
Foreword
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The committee responsible for this document is ISO/TC 21, Equipment for fire protection and fire fighting,
Subcommittee SC 8, Gaseous media and fire fighting systems using gas.
This third edition cancels and replaces the second edition (ISO 14520-8:2006), which has been
technically revised with the following change:
— added Clause 7.
A list of all parts in the ISO 14520 series can be found on the ISO website.
iv © ISO 2016 – All rights reserved

INTERNATIONAL STANDARD ISO 14520-8:2016(E)
Gaseous fire-extinguishing systems — Physical properties
and system design —
Part 8:
HFC 125 extinguishant
1 Scope
This document contains specific requirements for gaseous fire-extinguishing systems, with respect to
the HFC 125 extinguishant. It includes details of physical properties, specification, usage and safety
aspects.
This document covers systems operating at nominal pressures of 25 bar and 42 bar, superpressurized
with nitrogen. This does not preclude the use of other systems.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 14520-1:2015, Gaseous fire-extinguishing systems — Physical properties and system design —
Part 1: General requirements.
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 14520-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
4 Characteristics and uses
4.1 General
Extinguishant HFC 125 shall comply with the specification shown in Table 1.
HFC 125 is a colourless, almost odourless, electrically non-conductive gas, with a density approximately
four times that of air.
The physical properties are shown in Table 2.
HFC 125 extinguishes fires mainly by physical means, but also by some chemical means.
Table 1 — Specification for HFC 125
Property Requirement
Purity 99,6 % by mass, min.
–4
Acidity 3 × 10 % by mass (3 parts per
million), max.
–4
Water content 10 × 10 % by mass (10 parts per
million), max.
Non-volatile residue 0,01 % by mass, max.
Suspended matter or sediment None visible
Table 2 — Physical properties of HFC 125
Property Units Value
Molecular mass — 120,02
Boiling point at 1,013 bar (absolute) °C −48,09
Freezing point °C −101
Critical temperature °C 66,02
Critical pressure bar abs 36,18
Critical volume cm /mol 210
Critical density kg/m 573,6
Vapour pressure 20 °C bar abs 12,05
Liquid density 20 °C kg/m 1 218,0
Saturated vapour density 20 °C kg/m 77,97
Specific volume of superheated m /kg 0,197 2
vapour at 1,013 bar and 20 °C
Chemical formula CF CHF
3 2
Chemical name
Pentafluoroethane
4.2 Use of HFC 125 systems
HFC 125 total flooding systems may be used for extinguishing fires of all classes within the limits
specified in ISO 14520-1:2015, Clause 4.
The extinguishant requirements per volume of protected space are shown in Table 3 for various levels
of concentration. These are based on methods shown in ISO 14520-1:2015, 7.6.
The extinguishing concentrations and design concentrations for n-heptane and surface class A hazards
are shown in Table 4. Concentrations for other fuels are shown in Table 5
2 © ISO 2016 – All rights reserved

Table 3 — HFC 125 total flooding quantity
Tempera- Specific HFC 125 mass requirements per unit volume of protected space, m/V (kg/m )
ture vapour
volume
Design concentration (by volume)
T
S
°C
m /kg 7 % 8 % 9 % 10 % 11 % 12 % 13 % 14 % 15 % 16 %
–45 0,1497 0,5028 0,5809 0,6607 0,7422 0,8256 0,9109 0,9982 1,0874 1,1788 1,2724
–40 0,1534 0,4907 0,5669 0,6447 0,7243 0,8057 0,8889 0,9741 1,0612 1,1504 1,2417
–35 0,1572 0,4788 0,5532 0,6291 0,7068 0,7862 0,8675 0,9505 1,0356 1,1226 1,2117
–30 0,1608 0,4681 0,5408 0,6151 0,6910 0,7686 0,8480 0,9293 1,0124 1,0975 1,1846
–25 0,1645 0,4576 0,5286 0,6012 0,6754 0,7513 0,8290 0,9084 0,9896 1,0728 1,1579
–20 0,1682 0,4475 0,5170 0,5880 0,6606 0,7348 0,8107 0,8884 0,9678 1,0492 1,1324
–15 0,1719 0,4379 0,5059 0,5753 0,6464 0,7190 0,7933 0,8693 0,9470 1,0266 1,1081
–10 0,1755 0,4289 0,4955 0,5635 0,6331 0,7042 0,7770 0,8514 0,9276 1,0055 1
...