Design and Installation
October 2014 4-2 06-236115-001
4-2.2.1 Determine Minimum Use Concentration Required
A Class A surface fire hazard is one that involves ordinary combustible materials.
A Class B fire hazard is one that involves flammable and combustible liquids and flammable
gasses.
A Class C fire hazard is one that involves energized electrical equipment.
Table 4-1 shows the minimum design concentrations of HFC-227ea for Class A surface fires
and Class C fires. Refer to Table 4-3 for minimum design concentrations for hazards the involve
Class B fuels.
The minimum design concentration of HFC-227ea for Class A surface fires is 6.7 vol% in
accordance with the requirements of NFPA 2001, 2012 Edition Section 5.4.2.4. The minimum
design concentration for Class C fires is 7.0 vol% in accordance with the requirements of NFPA
2001, 2012 Edition Section 5.4.2.5. The classification of a hazard where electric power to
energized equipment has been turned off prior to discharge of the extinguishing system is
Class A.
Note: Where NFPA 2001, 2008 or earlier editions are enforced, it is acceptable to use the min-
imum design concentrations based on the requirements of the accepted edition. The
governing authority or authority having jurisdiction (AHJ) must specifically approve the
design approach selected.
4-2.2.2 Calculate the Volume of Protected Area
Calculate the volume of the protected area based on the length, width, and height, or geometry
of the hazard. This volume is used when calculating the quantity of agent required.
Table 4-1. HFC-227ea Fire Suppression Use Concentrations
Occupancy Fire Risk
HFC-227ea Minimum Design
Concentration, vol.%
Class A surface fires 6.7
Class C fires (fires involving electrically energized equipment) 7.0
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