Thu, 13 May 2010|
This short video from the Dublin Fire Brigade describes fire behavior in compartments and how to fight this type of fire.
Compartment. Fire fighting. Compartment firefighting techniques have evolved considerably over the last number of years. Dublin fire brigade has undertaken to keep pace with the changes. And is determined to follow best international practice in this very important area. This short film was designed not to replace hands on training. But to announce it. One of the -- of the film is to promote a deeper understanding of how far behaves in compartments. The main objective however -- is to discuss how to fight this type of fire. In the early 1980s. Followed the deaths of two Swedish firefighters. Techniques were developed by -- -- and -- Sunday. To protect firefighters from hazards associated with compartment fire fighting. These techniques involved recognition skills by firefighters. Of -- specific far characteristics. Allied with these skillful application of water pulses. These skills and tactics became known as offensive or 3-D fire fighting. These tactics were introduced in 1999. To Dublin fire brigade techniques have been refined over the years by the Swedish rescue services agency. And UK -- services this training film would reflect that development. Compartment fire behavior. Combustion is basically a chemical reaction -- fuel combines with oxygen. This reaction requires heat to enable it to work. Compartment fire behavior follows predictable development faces. These phases on initial fire growth period. Flash over a period fully developed fire -- -- period. Initial fire. -- -- needs three elements to propagate heat which is the energy. Few -- can be founded one of three states solid liquid or gas for flaming combustion to a -- the fuel must be in effect for a state. Oxygen. Fuel mixes with there and reacts with oxygen. Providing these three factors are present in the right proportion. Combustion -- When talking about five starts we use the term fire trigger. -- triggers the term used to describe the object that has caused the fire. Some examples of fire triggers. Electrical faults cooking -- Smoking. Arson. Growth period and. Our promises is -- chemical decomposition process -- -- if you move being exposed to heat. Our promises you speakers at a temperature range between 100 degrees Celsius to 250 degrees Celsius. I realized -- that start burning when there are mixed with oxygen. Some of the gases which accumulate at the surface of the fuel will not -- -- in the flames. This is because they are -- to rich. But because they have not reached their ignition temperature at this point these gases because they are a low intensity -- there. Will rise and -- -- smoking gun slayer in this evening. This compartment has sufficient oxygen for continued combustion. This type of -- development is known as a fuel controlled fire. Combustion in this room is controlled by the fumes properties and a few arrangement in the room. The -- gases found in a typical compartment -- and -- there are H two O water. CO2. Carbon dioxide. CO carbon monoxide. H two hydrogen. HCN. Hydrogen cyanide. And to nitrogen dioxide. That -- look at the characteristics. Of flame. -- -- -- -- Two types of flame. Diffusion flame. And pre mixed flame. In most compartment fires the visible flame is generally -- defused -- The fire -- normally occurs when it defused flames spread to crossed combustible material. Defused -- indicate less efficient combustion. This -- has a defined outline appears elongated. And occurs when the few and meet. As you can see the flame appears -- That -- it's ultimately defused flame is -- irony. -- flames are usually yellow or orange in color. -- results from a combustion process where if you -- -- so mixed with oxygen through -- are part turbulent mixing. -- to fusion flames have characterized by oxygen and fuel. Flowing side by side -- low velocity. They mix over a long period and produce smooth the long flowing play again a candle flame being a good example. When the rate at which the -- gases so floating is higher than that at which it is mixing with the oxygen the mixing process occurs in turbulent gases. This causes an irregular and on -- combustion resulting in the characteristic turbulent defused -- A pre mixed flame occurs -- the fuel and there are well mixed before a mission -- cars. The flames therefore -- and -- these claims can be blue in color. -- good example of a pre mixed flame is a punts and burner with the oxygen aperture open. These flames -- far more efficient combustion -- -- flames this can be measured in higher temperature output. And the amount of -- -- remaining on -- being dramatically reduced. Scenarios involving pre mixed gases often cause extremely hazardous situations operationally. We will discuss these in. Other factors affecting the growth phase. Passive nature and so. Passive so present in any combustion process. But take no part of the chemical reaction. They do however Steele heat energy and will affect the -- this development. Some examples saw. Carbon dioxide. Water vapor nitrogen. Ambient air temperature and humidity. The available oxygen supply. Determines the amount of on -- gases. The smaller the quantity of oxygen being supplied to the compartment the larger the quantity of on -- gases. -- geometry. If a fire starts in a corner. The wolves would reflect he's assisting the race in which the five develops. If a five stocks in the center of a room. The far will generally develop slower in this circumstance. And. -- little thermal inertia. This is simply a property of the available fuel. The larger the thermal panacea of a fuel the slower the flames spread. Generally the -- the fuel is. The higher the thermal and NCAA is on the higher its resistance to changes in temperature. And surface direction. Flames spread is mainly upwards. -- would spend as much slower. So that direction of the surface affected determines the growth rates of combustion. As the fire continues to develop the smoke there can be seen clearly in the upper part of the compartment. Because the smoke is less dense than the air in the compartment the smoke has risen and mushroomed across the occupancy. The -- of combustion is accelerating. Now producing even more paralyzed gases. The gases cannot escape the compartment in this case as quickly as they -- -- The gases and pressure rising to compartment. The smoking there cannot be cold and overt pressure area in the compartment. As the fire continues to develop. A significant amount to that they -- -- there is -- trained from the lower levels of the compartment. Towards the fire. The fire is consuming the oxygen in the air at a greater rate as it develops. This is zoned in the compartment because of the negative pressure being generated by the fire. Cannot be called the under pressure area. Where the over pressure and under pressure areas in the compartment equalize can be called the neutral zone. This area is in the vicinity of the smoke and there its effects. This is not the bottom of the smoke there but this can't be used as a general indicator the height of the neutral zone is a vital piece of information for firefighters. On opening -- -- compartment this should be evaluated as part of a dynamic risk assessment. We would return to this impeachment later and. Flash over a period. We can clearly see the flames starting to ignite the fire -- in the ceiling above the fire. This is the start of the flash over a period. That's not show for it is a transition period from where the -- -- is running locally until the whole room this fully involved. Flash over -- -- temperature -- event and usually occurs between 500 degrees Celsius to 600 degrees Celsius. The flash over a month the transition from -- five development to a fully developed compartment fire. And we told available fuel vapor is ignited. Fully developed fire. This stage is reached an influential for a -- At this point five -- temperatures can reach between 800 degrees Celsius to 900 degrees Celsius. Flames could spread to outside to -- -- -- -- openings. Some combustion can occur outside the compartment. Once a -- children has occurred -- -- the available oxygen of the remaining fuel will control -- if either oxygen or fuel is exhausted. The fire will decay. -- -- -- The -- period is the period after a fully developed compartment fire. At this stage the temperature starts to drop as the fuel is consumed. Recap. So we have seen that a compartment fire could develop in stages that are predictable and recognizable. Initial fire. Growth period. Flash over a period. Fully developed fire. -- period. The example we have just seen is a fuel controlled far. That is a fire that enough oxygen available for the -- development to be entirely controlled -- -- type dependency. We have also witnessed a flash over. The clash over is a transition period from when the -- was -- -- to sustained fully involved fire. Flash over it's -- temperature induced event. Signs of an imminent slash children's pool. Room temperature rises dramatic -- Rapid lowering of the neutral zone. Flames start to appear -- of the -- council there. Increased rate of paralysis. Flames start to spread across evening. This period can be very short sometimes as little as fifteen seconds and. -- -- Statistically only 3% -- ever become fully developed. 97% remain localized. -- so flammability. That's -- gospel only -- -- parent if its composition lines between certain limits. If too little too much fuel is present combustion will not take -- The mixture is then sent to be too rich or too lean. If -- look at the flammable range of propane we can see the guns will burn between two and 10% propane to -- mix. -- gas program. Efficiency that is with a maximum force and with the Foster and most intense combustion at 4%. This is known as the ideal mix. The efficiency of the combustion process will decrease but the -- concentration to air moves towards a leaner or -- a mixture. The lowest concentration of -- -- -- mixture that was just support a self propagating flame. This is known as the lower explosive limit. The highest concentration of fuel that would just support a self propagating flame this is known as the upper explosive limit. Flammability limits have a direct relationship to compartment fire fighting. Fire gases are fuel. Ventilation controlled fire. Specify develops the situation may develop weather is insufficient oxygen available to come bust the paralyzed gases that -- development does not -- determined. By the amount of oxygen available. This type of five development is known as a ventilation controls fire. It follows that the amount of oxygen available to the fire will determine whether the -- gases or rich won't mean. In some cases the fire may simply go out. If -- fire is ventilation controlled. And it's producing rich -- gases the introduction of oxygen perhaps by the actions of a firefighter. Will affect defies development. In some cases some -- gases would return to within flammable limits resulting in a violent return to a fully developed -- This could result in back dropped. Restricted ventilation during the development of the fire can result in the formation of a large quantity of rich and burnt gasses. If an openly -- through structural failure. For the actions of a fire -- the incoming and connects with the fire gases forming a combustible mixture somewhere in that room. If an ignition sources present that mixture may ignite violently causing the other gases to be pushed out through the opening. Producing a ball of flame outside the opening. This is a relatively rare phenomenon. That can be extremely hazardous to firefighters. About dropped -- a pre mix of fuel and oxygen prior to ignition. This results in a very efficient and sometimes violence combustion. Signs of potential -- dropped. Ventilation control fire. Thick black yellow or brown spoke. Blue flames. -- doors and windows so blackened windows. Lack of visible claim. -- being drawn in. The though neutral zone. Smoke pulsating. High velocity gravity current. And gravity current describes the phenomena visible up and opening -- a compartment but the fire gases are accepting and -- is being drawn -- A reliable indicator of -- ventilation control fire is the higher velocity of the far gases leaving the compartment when an opening has made. This in conjunction with other signs such as the thickness of the color of the fire gases can greatly assist in assessing the nature of the five development. Conversely a low velocity gravity current -- together with -- spoke is suing can be a reliable indicator over the fuel controlled fire. Find gas explosions. -- But five gases leaked into an -- -- compartment. There is a possibility that these gases may mix very well with the available oxygen. This pre -- may approach an ideal mix if an ignition source presents such as a light switch being activated. Or even a burning -- are turned over by a firefighter the -- may not -- -- -- resulting in a foreign gas explosion. This is an unusual phenomenon but the results can be devastating. -- Fire suppression techniques. And there are three basic brunch technique country agrees that made -- move to the fire fighter. Direct technique. The direct application of water on the seats up the fire is probably the oldest technique used five firefighters. The general quarters kept moving. The advantages of this technique that the fire can be fought from considerable distances. This technique is useful as an exterior tactic. The disadvantages are considerable and fire fighters are operating inside compartments however. Excessive amounts of -- produced making conditions difficult and dangerous -- -- firefighters and victim. Visibility in the for profit is compromised. The jet of water main break up the -- -- the fire resulting in -- spread. -- may in some cases in -- but dropped. Water runoff is considerable increasing water damage it. In direct technique. This technique was developed in the fifties in the USA. The technique involves using water phone with a wide cone angle the five butterflies the water and patterns of old half compartment surfaces. -- -- But PSV as an example. Don't -- -- this technique used to produce large quantities of steam to smother the fire. This is an extremely efficient method of fire suppression if the firefighter is outside the -- Because of the large amount of steam generation. Conditions inside the compartment would quickly become untenable for the firefighter. Visibility in the department would be in. Ideally this technique should be used in conjunction with tactical ventilation before crews -- the -- profit. We've discussed this technique letter. Offensive fire fighting. These techniques were developed in Sweden in the early 1980s. The techniques revolve around the concept of firefighters. Skillfully applying pulses of small droplets of water in the far gases whether the -- gas is too much as. -- not. -- -- -- Door entry. Safety zoning. Long pulses. Sweeps. Painting. Hydraulic ventilation. Let -- look at the basic skills of 3-D offensive fire fighting. Door entry. The point of entry to a building fire is the most dangerous opening fire fighter -- -- This is because on opening a door or window we are introducing oxygen to the fire. As we have learned this can affect the -- development in several ways he can change a ventilation control fire to a fuel controlled fire. Dramatically increasing the rate to -- release and exoneration development. We could induce backed draft. Correct door entry technique is vital. Observe how the two firefighters approached this. The -- operator takes up position -- using the walls has cover. The second firefighter establishes control of the door it is important that they coordinate their work to ensure safety. The -- -- places pulse of -- -- on the door. This will give an indication -- -- behind that door the firefighters look at other indicators before continuing. These indicators should include door paint blistering -- -- and windows. On a signal the second firefighter opens the door just enough for the French -- to CN. The firefighters have specific tasks. The -- operator should look below the neutral zone and try to determine the -- -- the fire and scanned -- casualties. The -- operated determines the height of the -- -- zone. At this point the crunch operator places -- -- supporter of into the overhead and listens to determine that the droplets vaporized or passed through could have -- gases and -- deceiving. The second firefighters closes the door quickly on the signal. On the door was opened the second firefighters observing the -- gases. He -- sent the thickness of the smoke and determine the velocity of the gravity current. The two firefighters -- fair. If the firefighters are not sure if they should repeat the process. Possible outcomes of the assessment. If there -- no -- -- indicators and the droplets did not vaporize than it is safe to enter. If there are no backdrop to indicators but the drop it's my -- -- you must change the conditions before entry. So how do you change the conditions. This can be done but -- using long pulses or sweeps after doing this you must close the door and repeat the temperature check. When the fire fighters decide to make entry they should quickly moved through the doorway. And a -- five gases -- in the department would be compressed through this opening making doorway and I'm comfortable point two remain. If there are signs of collapse however the doorway could be a place of relative safety. Firefighters must be vigilant. The -- -- must -- -- in front and overhead idle time it's. The second -- -- must observe behind and overhead constantly when the firefighters into the forest and -- They could find sense in -- claiming -- -- it is important that they make these gases inept and prevent the possibility of ignition. They do this using it technique known as safety -- This technique involves the firefighter. -- to branch almost vertical. The cone angle should be as wide as the compartment with -- making sure water does not hit compartment boundaries. The -- is very briefly opened about half way. The -- is never aimed at the same place twice. This maximizes the cooling effect in the -- guests the droplets of water -- -- testify against making them less likely to ignite. Similar techniques are employed. To extinguish burning -- -- that's. These techniques in conjunction with the education firefighters in compartment fire behavior that seems remarkable advances -- firefighters safety and efficiency. -- zoning has two functions one. Two in -- -- mom claiming five passes. -- to determine the temperature of the gases in the overhead. This information would assist firefighters in deciding if they should. Advance -- safe. Maintain position. Withdrawal to a safer place. If water droplets vaporized in the -- gases. This indicates that the gas temperature. Is -- excess of 100 degrees Celsius. Firefighters need to change these conditions before advancing -- firefighters cannot change these conditions. They should withdraw to a safer place. Two firefighters. Changed the five guys temperature. We Camilla defined -- temperature by using long pulses source sweeps. These techniques can also be used to do with flaming combustion. Long hoaxes. The basic technique is to apply the pulses into the -- -- avoiding water contact with a compartment boundaries. This results in several benefits to the fire -- -- -- within minutes and not -- Burning gases would be extinguished and contract away from the firefighters. The thermal balance of the -- would remain intact keeping -- higher compartment temperatures exceeding levels. This means that firefighters will be safer and more comfortable. Visibility in the compartment will be maintained assisting rescue operations. -- pulses are used to dealing with flaming combustion. The technique requires a narrower cone angle and tonight that indicated by roughly what the platform of the department -- the -- Felt the brush enough to apply the right amount of water. -- for the corners of the room. -- -- -- If you hear the water hit the ceiling you're aiming to -- If the flame from two huge expense towards you you're aiming to -- If the plane contracts away from you you're aiming in the right place. Apply less formal offer that's required. Let's you control the fire you -- defense towards the seat. If along pulses do not control the fine and should resort just weeks. You may -- ask how much water should be -- The answer is simple you should put on no more water than is needed to create the desired effect that a city. Too much excess of steam is generated department. -- feel -- the visibility dramatically disapproves. Too little. No significant effect on fire conditions. Correct amount conditions improve visibility remains good heat which uses. And sweeping. Sweeping as a technique that allows firefighters to -- larger area of the flaming well -- flaming combustion. Firefighters should utilize the number or -- Gold and slowly suite 180. Degrees holding the brunch at an angle about halfway between -- on the floor. This technique can be useful. To a -- -- gases before compartment entry in the ventilation controls fun. To change conditions if a safety zoning technique has indicated that gases in the open ahead on superheated. Painting -- when you get close to the seat of the -- you should fully extinguish the fire by painting. Painting involves setting -- -- to -- and using garden hose water pressure to paint we'll paralyzing surfaces. This will minimize steam production and water damage. When the fire is extinguished make radio contact with the -- -- see to determine inventing is appropriate. Never -- without permission it could be more than one compartment on fire and venting actions could create dangerous changes in conditions. The could be situations where firefighters may have to negotiate several smoke filled compartments to find the seat of the fire. It is imperative that firefighters. Safety zone their way through these compartments making their roots in about safe. The interior door entering technique. But going from one department to the next it is important that -- -- treat each department with the same caution. -- -- can be fuel controlled at one point the building and ventilation controlled in other compartments. Interior door entry technique varies from the exterior technique. Firefighters responsible for -- the -- combustible it's around or near the door. This reduces the chance of fires spread should -- combustion -- and country and opening the door. The interior door entry technique is identical to the exterior methods after taking this precaution. That drought mitigation techniques. This method involves firefighters identify the signs and symptoms before proceeding. Firefighters should notify polite -- their observations. And await instructions. In most cases the officer in charge will order an immediate evacuation of the building and he may also approved the following. Firefighters -- proceed to use and under pressure over pressure brunch technique. Elections must be coordinated carefully and in sequence. The -- directed into the over pressure region and along pulse is applied. The door closed the period of about ten seconds allowed elapse before reopening. Them alone pulse applied to -- under pressure. Water must be applied gradually in this instance it is better to apply to little slowly. Rather than too much quickly gradual application and ensure that the steam pressure Christians will not break the window. This could induce a backdrop. Why this is happening the only seat when -- decided -- to make the exhaust vent notice that the firefighters in a safe position. And -- covering brunch is in place. The exhaust -- behind in the structure and don't wind -- the in -- spent. The covering brunch must never be directed into the compartment at any point. When the -- is inside the compartment saturated steam. The crew should inform the officer in charge and the way construction. -- icu and ordered the exhaust vent to be made. Followed soon occupy. -- The -- will then be ventilated of superheated steam. As the fire returns to a few control -- fire the crew can enter safely and extinguish. This ventilation technique is known as tactical cross ventilation. Hydraulic ventilation and the French can be used to assist fun I guess ventilation by the firefighter. Setting up about two meters from the fence. And opening -- cone angle to cover 80% to prevent. Open it in that pent -- win. Some rooms for compartment fire fighting. -- firefighters committed to the pot pies should have a phone funding -- whether they're role as firefighting force search and rescue. A profit finest can be defined as -- as in enclosures or less than seventy square meters with astounded 2.3 meter ceiling -- Three deal offensive techniques and not as offensive into conference consciousness. If structural members of the house become involved or -- deceiving breaches without eating with the structural fire. Minimum flow rates compartment and the structural fires. For compartment fire fighting you need a minimum of 200 liters per minute. That's two -- -- -- This gives the five budget enough water should the fire develop unexpectedly. About up 45 millimeter coastline must always be made down from the second the rising pump and crews -- committed. This gives the cruise the safety margin and the original water -- proves inadequate to deal with the fun. Thank you for watching this dvd and should you have any further questions and please make them known to your officer in charge. Dublin fire brigade would like to acknowledge the assistance of the following the making of this vote. -- and -- -- set fire and rescue service. Swedish rescue services agency. -- Vonage college Essex County fire and rescue service. Fire services college Morton. -- -- --