ETL 1110-3-481
31 Mar 97
life of oxygen and cause fish kills. If allowed to enter the
sewage treatment facilities in relatively large volumes, AFFF
foam can disrupt the treatment process.
AFFF FIRE SUPPRESSION SYSTEMS
4.
The potential for, and magnitude of a foam system discharge from
a fixed fire suppression system largely depends upon the type of
system installed in the facility. Systems using "open" discharge
devices such as nozzle systems and deluge sprinkler systems, are
activated by a electronic control systems employing detectors,
manual release stations, and other types of alarm initiating
devices. Thus, "open systems" are susceptible to unwanted
discharges caused by false activation of flame and heat
detectors, power surges, physical damage, and accidental
activation of manual release stations. Closed systems, on the
other hand, are activated by the heat from a fire and are not
prone to false discharge.
Open Fire Extinguishing Systems
4.1
Open fire extinguishing systems have open orifices and consist of
monitor nozzle systems or overhead deluge sprinkler systems. To
activate, they require the operation of a detection system or
manual release station.
Nozzle Systems
4.1.1
Fire suppression systems utilizing fixed or oscillating nozzles
are provided in hangar which house large aircraft or aircraft of
strategic importance. They are designed for rapid application of
foam and are susceptible to unwanted releases of foam solution.
Depending upon the size of the hangar and aircraft being
protected, nozzle systems can be designed to produce discharges
of thousands of gallons per minute of foam solution.
Deluge Sprinkler Systems
4.1.2
In terms of discharge potential, deluge sprinkler systems are
comparable to nozzle systems. Both employ open discharge
devices, all of which flow upon system activation. Deluge
sprinkler systems are typically provided in large hangars in the
private sector. However, applicable Army, Air Force and Navy
criteria mandate the use of closed-head, not deluge systems, in
order to avoid clean-up associated with unwanted discharges.
A-6
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