Fire Safety OHS Lecture Notes PDF

FIRE SAFETY What is Fire?? 2 Fire is an exothermic combustion reaction which liberates large amounts of heat, smoke & light as main products of combustion Effects of Fire: → Heat causes burning of it...

FIRE SAFETY What is Fire?? 2 Fire is an exothermic combustion reaction which liberates large amounts of heat, smoke & light as main products of combustion Effects of Fire: → Heat causes burning of items and property and smoke causes suffocations and disable the visibility. → Environmental pollution → Loss of land and infrastructure. → Loss of biodiversity → Global warming → Water Contamination Common Causes of Fire 3 Carelessness: Disposal of cigarette butts in a trash bag. Smoking in bed at night. Leaving cigarettes burning in ash trays. Ignorance: Inadequate fire prevention Knowledge Accident : Electrical Short circuits etc. Sabotage: Deliberately destroy or damage. National Fire Protection Association (NFPA); Sign for Hazard 4 2 40 31 Flash Point: The temperature at which a particular organic compound gives off sufficient vapor to ignite in air How Fire Works?? 5 COOLING Cool Materials HEAT Chemical Chain Remove Reaction Fuel Fuel Smother Oxygen Source Air Supply Interrupt Reaction The fire triangle Fire Tetrahedron Fire cannot exist without all of these elements in place and in the right proportions Principles of Fire Extinction 6 1. Starvation 2. Smothering Removal of un- Cutting off the burnt material supply of oxygen from fire area from fire area 4. Break Chain 3. Cooling Reaction Removal of heat Stop or interrupt from the burning the chain reaction material or fire between the fuel, area heat and oxygen the fire will be extinguished.  Principles of Fire Control 7 Removing Heat Heat can be removed by the application of a substance which reduces the amount of heat available to the fire reaction. This is often water, which requires heat for phase change from water to steam. Introducing sufficient quantities and types of powder or gas in the flame reduces the amount of heat available for the fire reaction in the same manner. Removing Fuel Without fuel, a fire will stop. Fuel can be removed naturally, as where the fire has consumed all the burnable fuel, or manually, by mechanically removing the fuel from the fire. Fuel separation is an important factor in fire suppression, and is the basis for most major tactics.  Principles of Fire Control 8 Reducing Oxygen Without sufficient oxygen, a fire cannot begin, and it cannot continue. With a decreased oxygen concentration, the combustion process slows. Oxygen can be denied to a fire using a carbon dioxide fire extinguisher or a fire blanket. For example, covering a fire with a fire blanket removes the "oxygen" part of the triangle and can extinguish a fire. Cut-off The Chain Reaction The fire tetrahedron represents the addition of a component, the chemical chain reaction, to the three already present in the fire triangle. Once a fire has started, the resulting exothermic chain reaction sustains the fire and allows it to continue until or unless at least one of the elements of the fire is blocked. Source of Fire Fuel: 9 Chemicals - acetone, ether, methanol, etc. Gases - hydrogen, natural gas Plastics - PCs, cable insulation, research Flammable liquid-based products, equipment. such as paints and varnishes Paper and cardboard - packaging Wood - desks, benches Fabrics - chairs, blinds, clothing You… Plastics and rubber cleaning products Source of Fire Ignition/Heat: 10 Exterior and natural sources such as: i. Lightning ii. Electrical sources such as faulty or overloaded wiring, electrical panels, electrical equipment and appliances, and HVAC (heating/ventilation/air conditioning) systems iii. Proximity of combustible materials to a heat source such as portable heaters iv. Open flames such as candles and food warmers used during catered events v. "Interpretive fires" such as fireplaces, cook stoves, candles, blacksmith shops vi. Construction and renovation activities such as hot work e.g. welding and paint removal vii. Improper use, storage, and/or disposal of flammable liquids such as paint thinners viii. Smoking materials ix. Gas leaks Source of oxidizer: 11 A natural component of air @ 21% Oxidizers Enriched atmospheres, > 21% oxygen Liquids hydrogen peroxide, nitric  labs, oxygen storage acid, perchloric acid Situations where oxygen / air is more difficult Gases to control: Oxygen, fluorine, chlorine  Outdoors Solids  Automatic ventilation systems Metal peroxides,  Open doors or windows ammonium nitrate.  12 Differences between Fire and Explosion: An explosion is detonated. A fire cannot be detonated. An explosion occurs after compounds are exposed to heat or shock. A fire is initiated after being exposed to a heat source only. Because of how quickly the reaction occurs in an explosion, shock waves are produced. A fire does not produce shock waves. Similarities between Fire and Explosion: Both require oxygen. Both create heat and light. Both usually will damage the environment in which they occur. THE STAGES OF COMBUSTION Fire Development Process: 13 INCIPIENT STAGE: This is the first stage in the fire growth process, typically created by an outside heating source, such as an open flame or smoldering materials. GROWTH STAGE: During this stage, the fire grows fast or slow, depending on the fuel load, type of combustion and availability of oxygen. The growth stage is largely dependent upon the fuel load present. FLASHOVER STAGE: This is a transitional stage that takes place between the growth stage and the fully developed stage. Flashover is a phenomenon created by the thermal instabilities within a compartment. FULLY DEVELOPED STAGE: During this stage, the fire has reached its maximum potential and is only limited by the availability of oxygen. DECAY STAGE: During the final stage, the fuel load and oxygen decreases and the gases and temperature begin to cool. The fire will begin to put itself out if left alone and no more fuel or oxygen is introduced into the compartment. THE STAGES OF COMBUSTION 14 decomposition is occurring at the surface of the Growth Phase: up fuel to 10% of the decomposing Vapors from the products released decomposing fuel burning has progressed to the point have ignited where the fire is still small but generating sufficient heat Decay phase (has heat but flashover+fully developed stage no flame) Understanding the Fire 15 HAZARDS AND RISKS OF FIRE Smoke & fumes Breathing difficulties, asphyxiation, poisoning Heat & flames - up to 1250°C Burns Building debris Impact injuries, burns Injury while escaping fire Trips, falls, trampling The Spreading of The Fire 16 Heat transfer is a major factor in the ignition, growth, spread, decay and extinction of a fire. Fires can spread by four method: The Spreading of The Fire 17 During a fire heat transfer occurs by Conduction -transfer of heat within the material itself. Convection -transfer of heat by the physical movement of hot masses of air. Radiation -refers to the emission of heat in the form of electromagnetic waves. Ignition is the process of initiating self sustained combustion. The ignition temperature of a substance is the minimum temperature to which it must be heated for it to ignite. Flash point is the lowest temperature at which a liquid produces enough vapor to form an ignitable mixture. e.g., Diethyl ether (-45 oC), Methyl alcohol (11.1oC) Lower the flash point of a flammable liquid, greater the hazard  Fire Prevention System 18 There are two types of preventing system, it’s: i. Active Fire Protection ii. Passive Fire Protection Active Fire Protection (AFP): Active fire protection (AFP) is an integral part of fire protection. AFP is characterized by items and/or systems, which require a certain amount of motion and response in order to work.There are four categories of AFP: Fire Suppression Fire Extinguisher, Flame Extinguisher, Fire Hydrant, Fire Blanket Sprinkler Systems Quick Response, Standard Response Fire Detection Smoke Detector System, Heat Detector System, Fire Alarm System Hypoxic Air Fire Prevention Carbon Dioxide Gas System  Fire Prevention System 19 Passive Fire Protection (PFP): PFP attempts to contain fires or slow the spread, through use of fire-resistant walls, floors, and doors (amongst other examples). i. Fire-Resistance Rated Wall/Door ii. Firewall iii. Fire-resistant glass iv. Fire-resistance rated floors v. Occupancy separations Fire Classification 20 In firefighting, fires are identified according to one or more fire classes. Each class designates the fuel involved in the fire, and thus the most appropriate extinguishing agent. The classifications allow selection of extinguishing agents along lines of effectiveness at putting the type of fire out, as well as avoiding unwanted side-effects.  Stages of Fire 21 Blaze Initial Stage Stage Over 10 Minutes (0 Seconds to 10 Minutes) TIME FACTOR Incipient Stage Blaze Stage Class A 0 -10 Minutes Over 10 Minutes Class B 0 -1 Minutes Over 1 Minute Class C 0 - 30 Seconds Over 30 Seconds Class D Leads To a Fire in Another Class of Fire Fire Prevention 22 Be fire safety aware Use good electrical equipment Control ignition sources Proper Storage of fuels Do not block fire exits, call points/ extinguishers Fire Prevention 23 Fire Procedure - Evacuation 24 On hearing the alarm →Call security on 2333 to advise of the fire alarm – do not assume someone else has done it. →Do not delay your escape to collect belongings but if you can turn off equipment/close doors and windows as you leave then do so. →If necessary, check that internal doors are cool with the back of your hand before opening them →Do not use the lifts →If smoke is present then keep low to the floor to add your escape →Leave the building by the nearest available fire escape route. →Go to the assembly area and await instructions. Fire Procedure - Evacuation 25 On Exiting The Building → Report to designated assembly point promptly → Don’t block any Emergency Services route to the building → Report any missing colleagues to Fire Warden → Report any disabled persons left at Refuge Points → Remain at assembly point until advised otherwise → Do not wander off as it may be assumed that you are trapped in the building People with Disabilities →Need to be assisted by volunteers or nominated personnel →For special events ensure that disabled persons have been taken into account and an evacuation plan is in place Fire Emergency Response 26 R Rescue A Alarm C Contain E Extinguish Firefighting Decision Criteria 27 Know department emergency procedures and evacuation routes. Know locations of extinguishers in your area and how to use them. Always sound the alarm regardless of fire size. Avoid smoky conditions. Ensure area is evacuated. Don’t attempt to fight unless: Alarm is sounded. Fire is small and contained. You have safe egress route (can be reached without exposure to fire). Available extinguishers are rated for size and type of fire. Fire Extinguishers 28 A fire extinguisher, flame extinguisher, DISCHARGE LEVER PRESSURE GAUGE or simply an extinguisher, is an active (not found on CO2 extinguishers) fire protection device used to CARRYING DISCHARGE LOCKING PIN extinguish or control small fires, often HANDLE AND SEAL in emergency situations. It is not DISCHARGE HOSE intended for use on an out-of-control fire, such as one which has reached DATA PLATE the ceiling, endangers the user (i.e., no escape route, smoke, explosion DISCHARGE NOZZLE BODY hazard, etc.), or otherwise requires the expertise of a fire department. DISCHARGE ORIFICE  29 A Trash W ood Paper PRESSURIZED WATER A Trash W ood Paper Class “A” fires only. 2.5 gal. water at 150-175 psi (up to 1 minute discharge time). B Liquids Grease B Liquids Grease Has pressure gauge to allow visual capacity check. 30-40 ft. maximum effective range. C Electrical Equipment C Electrical Equipment Can be started and stopped as necessary. Extinguishes by cooling burning material below the ignition point.  30 CARBON DIOXIDE (CO 2) A Trash W ood Paper A Trash W ood Paper Class “B” or “C” fires. 2.5-100 lb. of CO2 gas at 150-200 psi (8-30 seconds discharge time). B Liquids Grease B Liquids Grease Has NO pressure gauge--capacity verified by weight. 3-8 ft. maximum effective range. Extinguishes by smothering burning materials. C Electrical Equipment C Electrical Equipment Effectiveness decreases as temperature of burning material increases.  31 MULTIPURPOSE DRY CHEMICAL A Trash W o o d Pap er Class “A”, “B”, or “C” fires. A Trash W o o d Pap er 2.5-20 lb. dry chemical (ammonium phosphate) pressurized to 50-200 psi by nitrogen gas (8-25 B Liquids Grease B Liquids Grease seconds discharge time). Has pressure gauge to allow visual capacity check. C Electrical Equipment 5-20 ft. maximum effective range. C Electrical Equipment Extinguishes by smothering burning materials.  A Trash W o o d Pap er A Trash W o o d Pap er 32 Class B-C fire, B Liquids Grease B Liquids Grease best choice for valuable electronics, no residue, easy clean-up Very short range, only 3 to 6 ft. Discharges quickly! (5 to 10 seconds!) HALON Use 1-2 second spurts C Electrical Equipment C Electrical Equipment Disperses quickly! Continue after flames are extinguished Halon weight-for-weight twice as effective as C02 Larger halon 1211 extinguishers are also rated class A  33 The main base chemicals used in DCP extinguishers Dry Chemical Powder(DCP) are sodium bicarbonate and potassium bicarbonate. DCP extinguishers puts out fire by coating the fuel surface with chemical powder. This separates the fuel from the oxygen in the air and prevent vapor formation. The powder also interrupts the chemical chain reaction of fire. The disadvantage is that it leaves residue particularly making it difficult to clean up in case of sensitive equipment. 34 35 Fighting the Fire 36 What’s A Fire Door? 37 Fire doors are designed to withstand fire, heat and smoke for a period of 20-minutes to 3 hours. Did you know that corridor office doors are fire doors and should have a 20 minute rating? Corridor laboratory doors should have a 60 minute rating. Fire Doors are required to: – Be Self Closing: fire doors should have a door closure that pulls doors completely shut after the door has been opened – Have Positive latching: a positive latch locks a door in place. Fire Protection and Prevention Safe Work Practices 38 Reporting and Extinguishing a Fire The fire department and area supervisor will be notified when a fire is spotted. All workers will be alerted and evacuated as needed. The PASS method will be used to extinguish the fire by those employees who have been properly trained. The area will be evacuated immediately if the fire is large. Fire Protection Before each project begins, the project manager or designee will contact the local fire department and determine whether any variations from the company’s standard fire-prevention procedures are required. Only approved containers will be used to store flammable or combustible materials. All containers will be grounded when transferring flammable or combustible liquids. All work areas will be kept free of debris and other combustible materials. Fire Protection and Prevention Safe Work Practices 39 Inside company-owned or leased buildings, fire extinguishers will be spaced no more than 100 feet apart and will have no less than a 2A rating for every 3,000 feet of protected building. No-smoking signs will be posted in all regulated areas. All employees will be trained on the use of fire extinguishers initially upon hire and annually thereafter. No employee will be permitted to use an extinguisher without having been fully trained. Fire Protection and Prevention Safe Work Practices 40 Fire Extinguishers In buildings, all fire extinguishers will be mounted on a wall and properly marked. All vehicles will carry at least one ABC-rated extinguisher. When at a job site, all employees will know the location of each fire extinguisher. Before using an extinguisher, all employees will be trained and familiar with the PASS method of firefighting. Each fire extinguisher will be inspected monthly to make sure it is in its designated location and has not been tampered with or actuated. Each fire extinguisher will be clearly visible with nothing obstructing or obscuring it from view. All fire extinguishers will be examined at least yearly and/or recharged or repaired to ensure operability and safety. A tag must be attached to show the maintenance or recharge date and the signature or initials of the person performing the service. Fire Protection and Prevention Safe Work Practices 41 Housekeeping Good housekeeping habits are an important part of a safe workplace. Why is good housekeeping important? To reduce amounts of flammable and combustible materials. To reduce ignition hazards. To ensure safe emergency evacuation of occupants. To allow for quick emergency response. Fire Protection and Prevention Safe Work Practices 42 Marking Sign For A Building Marking sign should consist of signs of similar size design and format. Their location should be consistent throughout the vessel. Emergency signs, including escape route markings, are rectangular or square with an approved photo luminescent pictogram on a green background. The sign must be at least 50% green/red/yellow/blue depend to function.There are a few types of sign in a building, it’s: i. Escape Route Sign ii. Fire Fighting Equipment and Location Sign iii. Escape Equipment Sign iv. Mandatory Fire Action Sign v. Mandatory Door Instruction Sign vi. Prohibition Sign vii. Hazard warning Sign Fire Protection and Prevention Safe Work Practices 43 Escape Route Sign Fire Fighting Equipment and Location Sign  44 REMEMBER ! Fire Prevention Is Everyone’s Responsibility and