- Количество слайдов: 43
FIRE SAFETY NEBOSH Certificate
FIRE SAFETY Aims to minimise consequences of fires • PREVENTION – make sure fires don’t start • PRECAUTIONS – minimise the damage from fire • PROCEDURES – action to take in the event of fire
HAZARDS OF FIRE • flames and heat • toxic/combustible smoke and gases • structural failure of buildings • oxygen depletion
FIRE TRIANGLE principles of combustion
Sources of fuel FLAMMABLE SOLID FLAMMABLE LIQUID FLAMMABLE GAS OXIDISING AGENT
SOURCES OF IGNITION - examples - Radiant or convected heat from heaters - friction - hot surfaces - chemical - sparks - smoking - electricity [static or mains] - internal combustion engines - tools - Flame
Principles of heat transmission and fire spread convection radiation conduction
Spread of fire • Conduction - spread of heat energy through solids; • Convection - heat transfer through a fluid or gas, involving expansion and movement; • Radiation - emission of heat energy through electromagnetic radiation in the infra-red part of the spectrum, which is then absorbed by matter to varying degrees
Extinction of fires • Remove one element or more of fire triangle, by: – starving it of fuel; – smothering it to exclude oxygen; – cooling it to reduce temperature. • Fire-fighting revolves around these principles
Causes of fires • • Arson discarded cigarettes and matches faulty plant & equipment flammable liquids & materials storage & use hot processes heating appliances combustible wastes Arson accounted for 41% of the 43, 600 fires that occurred in non domestic premises in 1999 [source: Home Office]
Art School molotovs
Elements of fire prevention and control
Interaction of fire legislation
The Building Regulations 1991: Approved Document B ‘Fire safety’ • Covers ‘means of escape’; internal fire spread (linings and structure); external fire spread; access and facilities for the fire service. • Requirements do not apply retrospectively, but will apply to new buildings, or modifications, etc to existing buildings
BS 5588 parts 1 – 11 Fire precautions in the design, construction and use of buildings • Escape routes – horizontal and vertical – Number of escape routes – Travel distances within each storey – Width of exits and escape routes – Number of persons per floor • Fire compartmentation • Fire resistance
BS 5588 -11: 1997 Escape distances
Fire compartmentation in buildings Fire escape route from various rooms are protected. office Office and classroom similar level of risk – no barrier. laboratory classroom Classroom protected from higher fire risks in laboratory.
Means of escape • ‘ A route that can be followed by an occupant, unaided or without risk from fire, that will lead to safety’ • clear marking of route, H’&Safety (Signs & Signals) Regs 1996 + BS 5499: 1990 ‘Fire safety signs, notices and graphic symbols, parts 1 & 3
Escape  • Calculated ‘Time available for escape’ greater than ‘Time needed for escape’ – time available calculated on assessment of time from fire start and its making escape route unsafe; – time taken for everyone to evacuate once the fire has been discovered & warning given. – More than one route - 25 m(HR), 32 m(Norm sleeping area), 45 m(NR), 60 m(LR); – One route - 12 m(HR), 16 m(NR sleeping), 18 m(NR except factories), 25 m(incl. Factories), 45 m(LR).
Escape  • Protected and unprotected zones • Escape distances [18 m hazardous processes, 45 m offices] • Fire compartments • Fire doors - self-closers, smoke seals, etc
Number & width of exits - Escape  • There should be enough available exits of adequate width, from every room, storey or building. Adequacy is assessed on: – doorways min. width 0. 75 m for upto 40 people/minute; – doorways min. width 0. 8 m for wheelchair users; – doorway min. width 1 m for upto 80 people/minute; – where more than 80 people/minute need to escape, the min. width should be increased by 0. 075 m for every additional 15 people. • Calculate above on the people in the building divided by the ‘time available for escape’
Building fabric - Building Regs 1991, Approved Document B • 0. 5 or 1 hour fire resistance of doors, walls and ceilings materials from which escape routes constructed; • Fire resistance of load bearing elements of structure; • Compartmentation, to reduce spread of fire, complementary to construction of escape routes; • Other - external fire spread, fire service access, ventilation
EVACUATION PROCEDURE - the recommended order of business 1. evacuate the building by the fastest route 2. sound the fire alarm 3. call the fire brigade 4. assemble at the designated location
FIRE DRILLS • legal requirement – effective means of escape • training exercise – practice evacuating the building by the fastest route and use of assembly points • test emergency procedures – role of fire marshals to aid evacuation and prevent re-entry
Fire Precautions Act 1971 • All premises meeting certain criteria must have a valid fire certificate; – hotels, boarding houses > 6 people, or bedrooms above/below ground floor; – workplaces, ie. Factories, OSRP premises • 20+ in workplace at one time, or; • 10+ above ground floor, or; • explosives or HFs stored or used • Cert. Issued subject to adequacy of escape routes, alarm systems, fire fighting equipment, etc
Fire Precautions (Workplace) Regs 1997 (99) • Require provision and maintenance of measures to detect, fight and warn of fires, ensure safe evacuation • Now, with MHSWR, require FRAs for premises • Revising FRAs ensures steady improvement, and covers buildings not included in FPA 71 and fire certificates
Building management of fire risks Good housekeeping by those responsible for managing buildings is a combination of: – Following fire risk assessment/Fire Certificate recommendations; – Constructing compartments, fire escape routes, and installing fire detection and alarm systems as necessary; – Reducing potential for fuels and ignition sources to mix; – Maintaining readiness to evacuate safely through organising staff, instruction and training, conducting fire drills and reviewing performance of people and systems.
BS 5839, part 1: 2002 - Fire detection and alarm systems • Manual - ie. People, who trigger the alarm system by activating a break-glass • Automatic - detectors placed carefully and sensitive to heat, smoke or combustion products
BS 5839 part 1: 2002 Fire detection and fire alarm systems for buildings • Purpose of fire alarm systems – protection of life and property; • System categories: –M Manual systems; – L [1 – 5] incorporate automatic fire detection to some degree, for the protection of Life; – P [1 – 2] incorporate automatic fire detection to protect Property.
Fire alarms • Triggered by automatic smoke or heat detectors or person activating a break-glass • Audible warning, klaxon or bell (can also be visual [flashing lights] for deaf, or vibrating pagers for deaf/blind) • can be shouting ‘fire!’ or hand-bell in small premises • Detection & alarm systems to comply with BS 5839: part 1
Classification of Fires - BS EN 2 • • • A - Free burning materials, paper, wood, plastics etc. B - Flammable liquids, petrol, meths, solvents etc. C - Flammable gases, methane, hydrogen etc. D - Metals, potassium, sodium, magnesium etc. Electricity can be involved in any class of fire
Water extinguishers Red body Suitable for use on Class A Fires, wood and paper etc. Not suitable for combustible liquids, cooking fats etc. Not safe to use on fires involving electricity; Extinguishes by cooling
Foam extinguishers Cream body (Old type) or Red Body with Cream label. Suitable for Class A and B Fires. Not suitable for use on fires involving electricity; Extinguishes by cooling and sealing the surface of a burning liquid.
Powder extinguishers Blue body (Old type) or Red body with blue label. Best on Class B fires but safe to use on any type of fire. Works by chemically interfering with the combustion reaction
Carbon dioxide [CO 2] extinguishers Black body (Old type) or red body with black label (New type). Best on Class B and C fires but safe to use on any type of fire; Safe to use on fires involving electricity; Extinguishes by reducing oxygen levels and cooling.
Other fire fighting equipment • • • Hose reels Fire blankets Automatic sprinklers Carbon dioxide/Halon systems Drenchers
HFL & LPG Regs - definitions • HFLs - flashpoint (below 32 o C) and combustibility. Test methods in schedules 1 & 2 of Regs. • LPG - commercial butane, commercial propane, or combinations thereof.
Storage • Suitable fixed storage tanks in safe positions; suitable closed vessels in open air and protected from direct sunlight; or closed vessels in storerooms in safe position or fire resisting structure; or in workroom in fire resisting cupboard which is fire resisting structure. Marking • Every storeroom, cupboard, bin, tank, and vessel used for storing HFLs should be clearly and boldly marked “Highly Flammable” or “Flashpoint below 32 o. C” • Where this is impracticable, such a warning is to be placed as near to storage as possible.
Precautions against spills and leaks • Conveyed through factory in vessels designed to prevent spills. • Process use to be kept as low as r. p. • Steps taken to prevent storage tanks from leaking. • Spills should be drained off to a safe place. Sources of ignition • No ignition sources shall be present where a “dangerous concentration of vapours from hfls is expected to be present. ”
Example references: • Fire Precautions Act 1971 • Fire Precautions (Workplace) Regulations 1997 [as amended] • Building Regulations 1991, Approved Document B ‘Fire Safety’ [not retrospective] • BS 5588 ‘Fire precautions in the design, construction and use of buildings’ [parts 1 -11] • BS 5839 pt 1: 2002 ‘Fire detection and alarm systems for buildings’