User's Manual

Design
September 2013 3-26 P/N 81-CO2MAN-001
3-6 LOCAL APPLICATION SYSTEMS
A local application system consists of a fixed supply of carbon dioxide permanently connected
to fixed piping with nozzles arranged to discharge directly into the fire where a permanent
enclosure about the hazard does not exist.
3-6.1 Carbon Dioxide Requirements
Local application design is based on three key factors:
• Nozzle location, orientation, and coverage area
• Rate of discharge
• Duration of liquid discharge
3-6.1.1 NOZZLE LOCATION, ORIENTATION, AND COVERAGE AREA
Since the concept of local application fire suppression is based on discharging suppressant
directly onto the burning fuel, the nozzle location, orientation, and coverage area are primary
factors in a successful system design. Each design approach, the Rate-by-Area method (See
Paragraph 3-6.2) or the Rate-by-Volume method (See Paragraph 3-6.3), has specific
requirements.
3-6.1.2 RATE OF DISCHARGE
Since local application systems do not retain an inert atmosphere beyond the end of system
discharge, it is extremely important to discharge carbon dioxide at a rate that is sufficient to
extinguish a flame, while refraining from spreading the fire.
The rate of carbon dioxide discharge is calculated either by the Rate-by-Area method (See
Paragraph 3-6.2) or the Rate-by-Volume method (See Paragraph 3-6.3).
3-6.1.3 DURATION OF LIQUID DISCHARGE
When a cylinder of carbon dioxide is discharged, a portion of the discharge will be liquid and
the remainder will be vapor. It has been found that only the liquid portion of the discharge is
effective in extinguishing fires by local application methods.
The minimum liquid discharge time for local application systems is 30 seconds (0.5 min).
However, the minimum time shall be increased to compensate for any hazard condition that
would require a longer cooling period to ensure complete extinguishment.
In the case where the fuel has an auto ignition temperature below its boiling point, such as
paraffin wax and cooking oils, the liquid discharge time shall be of a sufficient duration such
that the fuel is cooled below the auto ignition temperature. The minimum discharge time for
such fuels is 3 minutes.
WARNING
Personnel should be made aware of the hazards associated with the discharge
of carbon dioxide in local application systems. Hazards to personnel consist of
obstruction of vision and reduction in oxygen to a level that will not support life.
These hazards can be expected to occur not only in the immediate area of
discharge, but also in adjacent areas to which the carbon dioxide gas may
migrate. Appropriate alarms shall be used to alert personnel so that they may
be evacuated from the protected space prior to system discharge. Suitable
warning signs must be prominently displayed in clear view in the protected area
and at the point of entry into the protected area to alert people to the
asphyxiation properties of carbon dioxide.