Tuesday, May 3, 2011

FIRE FIGHTING SYSTEMS

AR-461: BUILDING SCIENCE
By:
RAVINDAR KUMAR
Assistant Professor
Department of Architecture and Planning
NED University of Engineering and Technology
Karachi
LECTURE NO. 27
TOPIC:                                                FIRE FIGHTING SYSTEMS

INTRODUCTION:[1]
Fire protection is the study and practice of mitigating the unwanted effects of fires. It involves the study of the behaviour, compartmentalisation, suppression and investigation of fire and its related emergencies, as well as the research and development, production, testing and application of mitigating systems. In structures, be they land-based, offshore or even ships, the owners and operators are responsible to maintain their facilities in accordance with a design-basis that is rooted in laws, including the local building code and fire code, which are enforced by the Authority Having Jurisdiction. Buildings must be constructed in accordance with the version of the building code that is in effect when an application for a building permit is made. Building inspectors check on compliance of a building under construction with the building code. Once construction is complete, a building must be maintained in accordance with the current fire code, which is enforced by the fire prevention officers of a local fire department. In the event of fire emergencies, Firefighters, fire investigators, and other fire prevention personnel called to mitigate, investigate and learn from the damage of a fire. Lessons learned from fires are applied to the authoring of both building codes and fire codes. In the United States, this term is used by engineers and code officials when referring only to active and passive fire protection systems, and does usually not encompass fire detection systems such as fire alarms or smoke detection.

GOALS OF FIRE PROTECTION:
Fire protection has three major goals:
  • Continuity of operations - on a public scale, this is intended to prevent the interruption of critical services necessary for the public welfare (e.g., a 911 emergency call center).
  • Property protection - on a public scale, this is intended to prevent area wide conflagrations. At an individual building level, this is typically an insurance consideration (e.g., a requirement for financing), or a regulatory requirement.
  • Life safety - the minimum standard used in fire and building codes

CLASSIFYING FIRES:
When deciding on what fire protection is appropriate for any given situation, it is important to assess the types of fire hazard that may be faced. Some jurisdictions operate systems of classifying fires using code letters. Whilst these may agree on some classifications, they also vary.

Below is a table showing the standard operated in Europe and Australia against the system used in the United States of America:


Type of Fire
Australia
European
North America
Fires that involve flammable solids such as wood, cloth, rubber, paper, and some types of plastics.
Class A
Class A
Class A
Fires that involve flammable liquids or liquefiable solids such as petrol/gasoline, oil, paint, some waxes & plastics, but not cooking fats or oils
Class B
Class B
Class B
Fires that involve flammable gases, such as natural gas, hydrogen, propane, butane
Class C
Class C
Fires that involve combustible metals, such as sodium, magnesium, and potassium
Class D
Class D
Class D
Fires that involve any of the materials found in Class A and B fires, but with the introduction of an electrical appliances, wiring, or other electrically energized objects in the vicinity of the fire, with a resultant electrical shock risk if a conductive agent is used to control the fire.
Class E1
(Class E) now no longer in the European standards
Class C
Fires involving cooking fats and oils. The high temperature of the oils when on fire far exceeds that of other flammable liquids making normal extinguishing agents ineffective.
Class F
Class F
Class K


Technically there is no such thing as a "Class E" fire, as electricity itself does not burn. However it is considered a dangerous and very deadly complication to a fire, therefore using the incorrect extinguishing method can result in serious injury or death. Class E, however generally refers to fires involving electricity, therefore a bracketed E, "(E)" denoted on various types of extinguishers.

Fires are sometimes categorized as "one alarm", "two alarm", "three alarm" (or higher) fires. There is no standard definition for what this means quantifiably, though it always refers to the level response by the local authorities. In some cities, the numeric rating refers to the number of fire stations that have been summoned to the fire. In others, the number counts the number of "dispatches" for additional personnel and equipment.

COMPONENTS OF FIRE PROTECTION:
Structural fire protection (in land-based buildings, offshore construction or onboard ships) is typically achieved via three means:

Passive fire protection (use of integral, fire-resistance rated wall and floor assemblies that are used to form fire compartments intended to limit the spread of fire, or occupancy separations, or firewalls, to keep fires, high temperatures and flue gases within the fire compartment of origin, thus enabling firefighting and evacuation)

Active fire protection (manual and automatic detection and suppression of fires, as in using and installing a Fire Sprinkler system or finding the fire (Fire alarm) and/or extinguishing it)
Education (ensuring that building owners and operators have copies and a working understanding of the applicable building and fire codes, having a purpose-designed fire safety plan and ensuring that building occupants, operators and emergency personnel know the building, its means of Active fire protection and Passive fire protection, its weak spots and strengths to ensure the highest possible level of safety)

BUILDING OPERATION IN CONFORMANCE WITH FIRE PROTECTION DESIGN:
The building is designed in compliance with the local building code and fire code by the architect and other consultants. A building permit is issued after review by the Authority Having Jurisdiction (AHJ).

Deviations from that original plan should be made known to the AHJ to make sure that the change is still in compliance with the law to prevent any unsafe conditions that may violate the law and put people at risk. For example, if the fire stop systems in a structure were inoperable, a significant part of the fire safety plan would not work in the event of a fire because the walls and floors that contain the fire stops are intended to have a fire-resistance rating, which has been achieved through passing a fire test and, often, product certification of the components involved in the construction of those walls and floors.

Likewise, if the sprinkler system or fire alarm system is inoperable for lack of knowledgeable maintenance, or if the building occupants prop open a fire door and then run a carpet through, the likelihood of damage and casualties is increased. It is vital for everyone to realise that fire protection within a structure is a system that relies on all of its components.


[1] Fire Protection; From: http://en.wikipedia.org/wiki/Fire_protection (Retrieved May 3, 2011)

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