In compliance with the
B.F.P.S.A. Code of Practice, enclosures protected against fire
by gas extinguishing systems must be provided with a means of
extracting the gas or post – fire atmosphere to open air.
Independent, normally closed, mechanical ventilation with
extraction provides the most efficient solution and for
liquefiable gases with high boiling points, such as FM-200,
the room atmosphere should be vented from low level.
As a means of complying with
this directive without the need to install a specialist
engineered system, GIELLE Fire Engineering are able to offer
the self contained VENTPAC extraction unit. Designed to suit
enclosure sizes up to 250m³ with or without voids, the
VENTPAC extract unit provides a minimum of four air changes
Simplicity of installation is
a major feature of VENTPAC. Contained within a Zintex metal
enclosure, the unit houses a high airflow centrifugal fan and
positive shutoff damper with motor and is very quiet in
operation. All components are electrically pre-wired to the
external terminal box for direct connection to remote
fireman’s switch or control facilities.
VENTPAC is complete with a telescopic transition duct,
requiring only a 250mm diameter aperture to be provided and
automatically allows for various external wall thickness
without the need for any specialist site fitting work. The
discharge duct terminates externally to a GIELLE got
connection fascia plate which is complete with a back draught
Dual path extract
Room atmosphere is extracted
through the louvered grille, positioned in the end plate of
VENTPAC. Where floor void extraction only is required, a quick
release baseplate can be removed and interchanged with the
extract grille. For situations where simultaneous room and
floor void extraction are required, partial removal of the
baseplate allows dual enclosure extraction.
Fixed fire extinguishing
systems employing inert gases extinguish fire by reducing the
oxygen content of the protected space. To achieve this, a
volume design concentration of 35% or more is normally
Injection of this high concentration results in a positive
pressure, which displaces the atmospheric air from the room.
To compensate for this over – pressure, system manufacturers
generally specify that suitable venting should be provided to
alleviate any risk of structural damage.
As part of the system design
programme, a calculation is made for the appropriate system
size, of the venting area required to prevent any damaging
over – pressurisation. System manufacturer tests and data
have established that normal build rooms will withstands an
increased pressure of 5mb (500 Pascals).
Any a means of complying with these requirements, GIELLE Fire
Engineering are able to offer the PRESPAC pressure relief unit.
Specially designed for use with fixed gas extinguishing
systems PRESPAC will open automatically when the positive
pressure reaches 1.5 mb (150 Pascals). As pressure equalises
the weighted relief blades close to seal the enclosure and
maintain the extinguishing concentration.
The BFPSA Code of Practice
stipulates that rigid elements of the protected enclosure must
have a fire resistance of not less than 30 minutes. Often to
comply with this directive it is necessary to install a
separate fire damper, in addition to the pressure relief unit,
which in the event of operation defeats the object of fitting
any over pressure device.
PRESPAC will maintain fire wall integrity without the need to
fit a separate damper. The unit has been independently tested
by Chiltern Fire to the general requirements of BS478: Part
20: 1987, where it achieved over two hours integrity.