• Housekeeping hazards: Piles of
scrap, waste materials, and trash; Sawdust, metal or plastic powder that can form an
explosive mixture with air; Obstructed aisles, Blocked emergency exits, Material
covering up fire extinguishers, exit signs, and alarms; Blocked sprinkler heads.
• Friction hazards: Hot bearings,
Misaligned or broken machine parts, choking or jamming materials, Poor
adjustment of moving parts, Inadequate lubrication.
• process or operation-related
hazards: Cutting and welding operations, which use open flames and produce sparks;
Molten metal, which can ignite combustibles or fall into cracks and start a fire that
might not erupt until after the work is done; Processes that heat materials to high temperatures;
Drying operations where materials in dryers can overheat;Grinding operations that produce sparks
and dust; Processes in which flammable vapors are released.
• Storage hazards: Materials
stacked too high blocking sprinkler heads (need 18-inches clearance from head); Flammable
or combustible materials stored too close to heat sources; Flammable materials not
stored in special containers and cabinets Inadequate ventilation in storage areas;
Materials that might react with one another stored together;Materials stored in damaged
containers; Materials stored in unlabeled containers;Containers not tightly sealed
• Smoking hazards: Ignoring
"No Smoking" signs; Smoking around flammable or combustible materials; Throwing
matches and cigarettes or cigars on tables or workbenches; Tossing butts on the
floor or grass without properly extinguishing them in an ashtray or ash can; Tossing
lighted butts or matches out windows or doors; Smoking in bed; Leaving a cigarette/cigar
unattended; Smoking in areas where there is an accumulation of sawdust, plastic or metal powders
that may become explosive.
Various types of Fire-resisting
construction:
The type and age of construction
are crucial factors to consider when assessing the adequacy of existing escape routes. To
ensure the safety of people it may be necessary to protect escape routes from fire. In older
premises it is possible that type of construction and materials used may not perform to current fire
standards and refurbishments may have led to:
• Cavities and voids being
created, allowing the potential for the unseen spread of fire.
• Doors and hardware being worn
by age and movement being less likely to limit the spread of fire and smoke.
• Damaged or insufficient cavity
barriers in modular building construction (e.g.CLASP or SCOLA type
construction).
• Breaches in fire compartment
walls, floors and ceilings created by the installation of new services, (e.g. computer
services).
Where an escape route requires
the provision of fire resisting construction (e.g. dead end corridors or protected stairways)
the following should be ensured:
• Doors (including access hatches
to cupboards, ducts and vertical shafts linking floors), walls, floors and
ceilings protecting escape routes should be capable of resisting the passage of flame
and smoke for long enough for people to escape from the building (normally 30 min).
• Where false ceilings are
provided, fire resistance should extend up to the floor slab above (for means of escape
purposes 30min fire resistance is required).
• Cavity barriers, fire stopping
and dampers in ducts are appropriately installed as required.
Fire resisting properties of common
building materials:
Fire resisting properties of
common building materials such as stone, brick, glass, steel and concrete are described below:
a. Stone: stone is a bad
conductor of heat and it is also a non-combustible material;however, it suffers appreciable
under effect of fire. Moreover, the stone is also liable to disintegrate in to small pieces
when heated and suddenly cooled.
b. Brick: Bricks are not
seriously affected until very high temperatures around 1200 oC to 1300 oC are reached. This is due
to the fact that a brick is poor conductor of heat.
c. Cast-iron: The material
files in to pieces when heated and suddenly cooled. Therefore,when this material in
construction. It is covered either by brickwork of one- brick thickness or any other fire
resisting material such as construction.
d. Timber: Generally, the
structural elements made of timber ignite and get rapidly destroyed in case of fire. To
increase the timber more fire resisting, the surfaces of timbers are coated with chemicals
such as ammonium phosphate and sulphate, borax and boric acid, zinc chloride.
e. Glass: The materials
are poor conductor of heat and its expansion due to heat is small.The cracks are formed in this
material when heated and suddenly cooled.
f. Wrought-
iron: This
material is rarely used as structural as present. It behaves more or less in the same way mild steel.
g. Aluminium: Very good
conductor of heat, it possess poor fire resisting properties.
h. Asbestos
Cement: this
is non-combustible building material with low coefficient of expansion. It therefore possesses high fire
resisting property than other material.
Characteristics of fire resisting
materials:
• The composition of the material
should be such that it does not become disintegrated under the effect of great heat.
• The expansion of the material
due to heat should not be such that it leads to instability of the structure.
• The contraction of the material
due to the sudden cooling with water after it has not been heated to a high temperature should not be
rapid.
Fire Protection
System: The
system which protects a large area from fire by using components such as pipes, pump
sets, control panel, sprinklers or nozzles etc,, is known as fire protection system.
1. Automatic
sprinkler system: Most
reliable automatic means of fire fighting. It involves automatic sprinklers attached to
a piping system containing water under pressure and connected to a water supply so
that water is discharged immediately sprinkler opened by fire.
2. Carbon
dioxide system: It
extinguishes fire by diluting flammable mixture of air and flammable gas or vapour to
proportions below their flammable limits.
3. Dry Chemical
system: This
system includes a supply of dry chemical, an excellent gas such as compressed nitrogen
detection devices, release mechanism, fixed piping and nozzles for discharging the dry
chemical into hazard area.
4. Foam System: In this system,
the mechanical foam is formed by passing foam producing liquid and water through adequate
device. The foam is as aggregate of air filled bubbles.It is lighter than flammable
liquids and oils. The principal components of this system include proportioning apparatus,
concentrated storage tank, water supply, foam maker or spray foam-heads, heat detecting
devices, automatic and manual actuation devices and an alarm system.
5. Holon System:
This
indicates a specific family of chemicals which are produced by replacing one or more hydrogen
atoms with halogen atoms. This is contained in cylinders under pressure in liquid state
and it is released through nozzles on piping distribution arrangement. An actuator is
provided a cylinder control value and it is operated either by electric or pneumatic signal when
fire occurs.
6. Hydrant
system:
in this system, the hydrants are located at suitable points and they can be operated at suitable points
and they can be operated manually or automatically.
7. Water Spray
System:
The water spray system used for fire extinguish depends upon the type of spray and can be sprayed
in two categories:
• Multi-fire system: water is
sprayed in high velocities
• Protective System: Fine water spray of low
discharge velocity
Some Construction Techniques of Fire resisting for Building:
Fire resisting wall
construction
The fire resistance of a wall or
floor is dependent on the quality of construction and materials used. Common examples
of types of construction that provide 30-minute fire resistance to escape routes if
constructed to the above standards are:
• Internal framed construction
wall, non-load bearing, consisting of 72mm x 37mm timber studs at 600mm centres and
faced with 12.5mm of plasterboard with all joints taped and filled.
• Internal framed construction,
non load- bearing, consisting of channel section steel studs at 600mm centres faced with
12.5mm of plasterboard with all joints taped and filled;
• Masonry cavity wall consisting
of solid bricks of clay, brick earth, shale, concrete or calcium silicate, with a minimum thickness of
90mm on each leaf. There are other methods and products available that will
achieve the required standard of fire resistance and may be more
appropriate for the existing construction in your premises.If there is any doubt about how
your building is constructed, then ask for further advice from a competent person.
Fire-resisting
floors
The fire resistance of floors
will depend on the existing floor construction as well as the type of ceiling finish beneath. If you
need to upgrade the fire resistance of your floor it may not be desirable to apply additional
fire resistance to the underside of an existing ornate ceiling.In older buildings there may be a
requirement to provide fire resistance between beams and joists.A typical example of a 30-minute
fire-resisting timber floor is tongue and groove softwood of not less than 15mm finished
thickness on 37mm timber joists, with a ceiling below of one layer of plasterboard to a
thickness of 12.5mm with joints taped and filled and backed by supporting timber.There are other, equally valid,
methods and products available for upgrading floors. If you are in any doubt you should ask
the advice of a competent person and ensure that the product is installed in
accordance with instructions from the manufacturer or supplier.
Fire resisting
glazing
The most common type of
fire-resisting glazing is 6mm Georgian wired glazing, which is easily identifiable. Clear fire-resisting
glazing is available and can quickly be identified by a mark etched into the glass,
usually in the corner of the glazed panel, to confirm its fire resisting standard.Although this is not compulsory,
the marking of glass is supported by the Glass and Glazing Federation, you should check
whether the glazing would be marked accordingly before purchase.The glazing should have been
installed in accordance with the manufacturer’s instructions and to the appropriate standard,
to ensure that its fire-resisting properties are maintained.The performance of glazed systems
in terms of fire resistance and external fire exposure should, wherever possible, be
confirmed by test evidence. Alternatively, where there is a lack of test information, ask for
an assessment of the proposed construction from suitably qualified people.
0 Comments
For more Information Please Comment