Fire Design: Fire Resistance Testing, Flammability Limits and Heat Release Rate - Coursework Example

FIRE DESIGN ASSIGNMENT [NAME] [INSTITUTIONAL AFFILIATION] [DATE] Table of Contents Table of Contents 1 Part A 3 Fire Resistance Testing 3 Reaction to Fire Testing 3 Flammability Limits 4 Heat Release Rate 6 Factors which Influence Fire Development & Rate of Fire Growth within A Compartment 7 PART B 10 References 22 Part A Fire Resistance Testing Fire resistance Testing is aimed at determining the ability of a building construction to withstand a given temperature when exposed to fire at a given time and specific pressure and retains its fire separating functions. The test may be carried out on some of the building parts such as the walls, ceiling, columns, beams, and the doors. The test is conducted as illustrated herein. The section to be tested, such as the wall, is placed horizontally or vertically on either side of an oven. Temperature recorders are then placed on the outside of the material to record the temperatures of the assembly. The flames are directed at the wall in question and penetrate the wall. The wall that is not protected will definitely collapse while the one that is protected will resist the collapse and remains firm (Sultan, Seguin & Leroux 1998).  Reaction to Fire Testing Reaction to fire testing may be defined as the measurement of how a system contributes to the development of fire and the spread of the fire. This majorly occurs during the early phases of a fire breakout when evacuation is of great concern. Reaction to the fire testing is important because it easens the rate at which people evacuate the fire areas. Reaction to fire testing is of so much concern to meet the laid down regulations of the building. Reaction to fire may relate to the combustibility and ignitability of a material, for example, its contribution to fire development and spread. Reaction to fire tests is in most cases called up in regulations both in the building and the transport industry (Redsicker & O'connor 1997).  Flammability Limits Flammability limits is defined as the range of composition for the fixed pressures and temperatures inside which explosive response is probable when the external ignitions are brought to effect. The limits are given in connection to the concentration of the fuel by volume at a given specified temperature and pressure. Flammability limits are not only absolute but also depends majorly on the strength and the type of the ignition source. Research indicates that the stronger the stimulus being ignited, the leaner the mixture. Type of the atmosphere and the pressure also determines the flammability limits, for example the flammability limit is much wider in oxygen than it appears in air (Barraclough 2008). Temperature effects on the flammability limits. It is well known that with the increase in temperature, the flammability limit also increases. The understated equations can be put into use to illustrate the effect of temperature on the flammability limits (Rau 2010). LFLT=LFL25*[1-(0.75/Hc)*(T-25)] UFLT=UFL25*[1+(0.75/Hc)*(T-25)] Where ; Ht = heat of combustion & T i=the test temperature. Flammable material temperature measured LFT calculated LFT measured UFL calculated UFL benzene 25.0 N/A 1.130 N/A 5.470 benzene 50.0 1.100 5.60 benzene 100.0 0.95 1.050 6.10 5.860 benzene 250.0 0.70 0.880 7.40 6.640 toluene 25.0 N/A 0.920 N/A 5.390 toluene 50.0 0.90 5.50 toluene 100.0 0.80 0.860 5.80 5.720 Toluene The temperature effect on the lower & upper explosive limit of toluene is illustrated in the diagrams below. The graphs indicate that the experimentally established of the extremely established figures of higher explosive values in the temperature limits are above the figures determined by empirical equations. For the lower explosive range it can be viewed that calculated figures from equations are much below the values calculated by the experiment and are seen to lie outside the explosion range calculated from the measured figures. Heat Release Rate Heat release rate measurements are most of the times seen by most people as a piece of data to gather. The single most vital variable in characterizing ‘flammability’ of the products and their eventual fire hazard. Examples of fire histories illustrate that even though the fire deaths are majorly caused by toxic gases, the rate at which heat is released is the major predictor of fire hazard. Conversely, the toxicity of the burning gases plays a less significant role. The delays in the ignition time, as can be measured by different Bunsen burner tests, also have only a lesser significant effect on the fire hazard. Fire safety of a performance-based design is most of the times evaluated by use of deterministic analysis. In this type of analysis, a given number of representative fire scenarios, and the design fire scenarios, are analyzed then a quantitative description then follows. The assumed fire characteristics are termed as design fire, for example there is only a design fire in connection with every design fire scenario. A design fire in most occasions defined with respect to the heat release rate, toxic species available, and the rate of smoke production. This report gives an exhaustive guidance in the selection of the design fires and it must be a vital resource for the fire protection personnel working with analyses that involve design fires. The report outlines a step-by-step operation method in which design fires are selected and outlines the factors that affect the design fire. Factors which Influence Fire Development & Rate of Fire Growth within A Compartment 1. Remote ignition This refers to the sudden ignition brought about by auto ignition or piloted ignition, contributed by the flaming brands, due to the radiant heating. The radiant heating is primarily from the compartment ceiling and the hot upper gases because of their large extent. The required threshold for the piloted ignition of many materials is about 20 kW/m2. This value of flux, is measured at the floor, and is majorly taken as an operational criterion for the flashover. It equally relates to gas temperatures of 500–600 C. Phases of fire development 2. Rapid flame spread The radiant preheating of the material may the surface temperature of a material to move towards the piloted ignition temperature. This may cause flammability limit to happen a head of the surface flame, which may cause a singularity in the simple flame theory hence causing a very rapid outcome, which may be in the order of 1m/s. 3. Burning instability Without fire spreading away from a burning item, the sudden fire eruption may be identified under the right conditions (Drysdale 1999). In this case, the thermal feedback that exists between heated compartment and the burning object may really cause a ‘jump’ from the initial stable state of the burning at the unheated, and the ambient conditions to the new stable state after the heating of compartment and the burning of the fuel come to the equilibrium. 4. Oxygen supply This mechanism promotes back draft. this involves a fire burning in a very much ventilation-limited state. The sudden breakage of a door or a window of the opening allows fresh oxygen to move along the floor. When this mixes with the fuel-rich hot gases, there is a sudden increase in combustion. This takes place so rapidly that a significant pressure increase may occur that causes the walls and the other windows to fail. It may not be like a premixed gas ‘explosion’. 5. Boil over This is a phenomenon that takes place when water is sprayed on a burning liquid, which is less dense, and with a boiling temperature which is higher than that of the water. Water droplets falling through the surface may then become ‘instant’ vapor, with a very significant expansion that may cause the spraying out of the liquid fuel. The increase of the area fuel spray creates a rapid increase in the fire. This may not really happen at the surface but may also occur at the collection of the denser water at the bottom of a fuel tank then suddenly boil as the fuel mixture recedes to the bottom which translates to the term ‘boil over’. 6. Surface geometry Considering different surface geometries, there is an interaction between the two surfaces that that is burning and this increases the rate at which the fire spreads. the flame spreads very fast with decrease in the angle. This is because heat gets trapped within the corner making the material to get heated up rapidly. The formed smoke gases heat u resulting in to a small percentage of air getting sucked into the plume. 7. Surrounding environment With the increase in the ambient temperature, the flame spread rate also increases. The material’s surface is heated up until ignition temperature is reached which occur so quickly. As the temperature increases from the start, the flame spread rate also increases so fast. Another result of this is that when a material has a higher temperature from the start, the surface produces enough combustible gases, which increases the burning rate of the material. PART B (The questions in this section are answered using the Approved Document B) 1. Five Functional Requirements of Approved Document B Approved Document B entails five functional elements, which include (GREAT BRITAIN 2007): a. The means both warning and escape b. Spread of fire internally as a result of the linings c. Spread of fire internally due to the structure d. Spread of fire externally e. The access and even the facilities used for the purpose of fire service 2. Definition of Means of Escape from Fire Means of escape from fire refers to any device or structure, for instance the outside stairway that is attached to a building or any structure that is elected for emergency exits in case there is fire. Main Requirements of Safe Means of Escape from a Building A safe means of escape requires a number of requirements. It requires an alternative means of escape in case of fire. The escape should be direct to the place of safety and if not possible, the escape route should allow access to an area of relative safety. A stairway that is protected and which lies on an exit route and travel distance should be reasonable. Some conditions require the existence of a single escape direction for provision of reasonable safety. 3. Maximum Recommended Size of Compartment (a) A single storey shop with sprinkler protection There is no limit as to floor height of the top storey for the building above the ground level. The floor area has not limit. (b) A single storey industrial unit For a single storey industrial unit that is sprinkled or not sprinkled, the maximum height is 18m. Further, there is no limit in terms of floor area. 4. Maximum size of an opening (unprotected area) that can be discounted when considering space separation between buildings The separation of the building from the boundary should be at least ½ the distance at which total intensity of thermal radiation is received. 5. identify whether a fire fighting shaft and lift are needed in the following types of compartments. An office building with a top occupied floor of 250m2 situated at a level of 19m above fire service vehicle access level Both a fire-fighting shaft and a lift are recommended for use is such a building component. They are used as a means of escape & to help fire fighters access the facility in case there is an outbreak of fire within a compartment, and to help rescue individuals within the compartment during the emergencies. A four storey assembly building with a top storey of 1400m2 that is situated at 10m above fire service vehicle access level Is it not really necessary to have a fire fighting shaft and lift for such building components of less heights for vacating such buildings in case of emergencies is easier. 6. Identify the recommended minimum fire resistance periods for the following compartments? a) What is the recommended minimum fire resistance periods for a 35m high sprinkler protected residential building? The recommended minimum fire resistance is approximately 30 minutes b) What are the recommended minimum fire resistance periods for a four storey shop with sprinkler protection? The recommended minimum fire resistance is approximately 60 minutes 7. Identify the various purpose groups that would be appropriate for the following types of structures. a. A students union building structure A student’s union building structure can be classified under the purpose group of 2(a) residential (institutional) purpose group b. A department store structure A department store structure can be classified under the purpose group of 7 (a) storage & other non-residential c. A factory structure A factory structure can be classified under the purpose group of 5 d. A swimming pool building structure e. A swimming pool building structure may be classified under the purpose group 5 majorly for assembly & recreation 8. Considering the Table 2 of Approved Document B provided, identify the various recommended travel distance limitations especially for the single direction & more than one direction for the following types of structures and facilities. What is the travel distance limitation for a normal hazard storage structure? The travel distance limitation is 25m for one direction and the travel distance limitation is 45m for more than one travel direction What is the travel distance limitation for a place of special fire hazard? The travel distance limitation is 9m for one direction & the travel distance limitation is 18 m for more than one travel direction. What is the travel distance limitation for a bedroom of an apartment? The travel distance limitation is 9m for one direction & the travel distance limitation is 18 m travel direction that is more than one What is the travel distance limitation for a lecture theatre with fixed seating in rows? The travel distance limitation is 15m for one direction & the travel distance limitation is 32 m for more than one travel direction What is the travel distance limitation for a Shop floor? The travel distance limitation is 18 m for one direction and the travel distance limitation is 45 m travel direction that is more than one What is the travel distance limitation for a Plant room that exits through the accommodation within a building? The travel distance limitation is 9m for one direction and the travel distance limitation is 35 m travel direction that is more than one 9. According to Table 3 of Approved Document B, identify the various recommended minimum number of escape routes from a storey with: 10 people-only one escape routes is needed in case of an emergency within a structure. 200 people –two escape routes needed in case of an emergency within a structure. 450 people - two escape routes needed in case of an emergency within a structure. 650 people - three escape routes needed in case of an emergency within a structure. 10. According to Table 4 of Approved Document B, what is the minimum exit width required to accommodate: a. For 219 people The minimum recommended width is 1050 mm b. For 61 people The minimum recommended width is 850 mm c. For 10 people The minimum recommended width is 750 mm and can be reduced to 1050mm in the case of gangways that lie between fixed storage rackings. d. For 500 people The minimum recommended width is 5 mm per person 11. A building with four above ground floors is served by two escape stairs without lobby protection. Using Table 7 of Approved Document B, identify the various minimum widths of the escape stairs if each floor accommodates the following number of people. a. What is the minimum width of the escape stairs for a floor containing 75 individuals? The minimum recommended width is 1000 mm for a floor containing 75 persons b. What is the minimum width of the escape stairs for a floor containing 130 individuals? The minimum recommended width is 1200 mm for a floor containing 130 persons 12. A building with five above ground floors is served by three escape stairs with lobby protection. Using Table 7 of Approved Document B, what is the minimum width of the escape stairs if each floor accommodates: a. What is the minimum width of the escape stairs for a floor containing 155 individuals? The minimum recommended width is 1500 mm for a floor containing 155 persons b. What is the minimum width of the escape stairs for a floor containing 230 individuals? The minimum recommended width is 1800 mm for a floor containing 230 persons 13. Assuming 100 occupants from the ground floor accommodation also exit through the ground floor of the stair enclosures for Questions 11 and 12, how wide do the final exits need to be? (i.e. a merging flow – diagram 15 and associated equation). When the number of occupants exiting the ground floor is assumed to be 100, then the final exit route may be calculated as indicated below ( 27 x 2) which translates to 54 Therefore the number of occupants equals to (54+100) =154 occupants Considering the provided table and document B; Therefore, the final exit, according to Approved Document B corresponds to a total width of Total minimum width of 1050 mm 14. According to Table C1, identify the floor space factors that would be most appropriate in the following areas? a. Identify the floor space factors that would be most appropriate for an office The most appropriate floor space factor is approximately 6.0 m2 for every person within the compartment. b. Identify the floor space factors that would be most appropriate for a bar The most appropriate floor space factor is approximately 0.3 m2 for every person within the compartment. c. Identify the floor space factors that would be most appropriate for a shop The most appropriate floor space factor is approximately 2.0 m2 for every person within the compartment. d. Identify the floor space factors that would be most appropriate for a students union The most appropriate floor space factor is approximately 1.0 m2 for every person within the compartment. 15. For a square room, 40m by 40m, calculate the number of occupants using the floor space factors obtained in Question 14. In each case what is the minimum number of exits required and how wide should each exit be as a minimum. Areas = 40 x 40 translating to a total area of 1600m2 The number of occupants will be as follows, depending on the floor space factor: An office = 1600/ 6 m2/ person translating to a total area of 267 persons A bar = 1600/ 0.3 m2/ person translating to a total area of 5333 persons A shop = 1600/ 2.0 m2/ person translating to a total area of 800 persons A students union = 1600/ 1.0 m2/ person translating to a total area of 1600 persons 16. What is meant by the following terms: a. What is meant by Life safety? Life safety can be defined as the satisfactory measures that are put in place for limiting harm to a person within a compartment in case of an outbreak of fire within such structures which may be due to smoke, heat, or firefighting waters. b. What is meant by Property protection? Property protection is defined as the satisfactory standards that are meant to limit the damage to building contents within a compartment during fire outbreak in order to save the structure components, the people inhabiting the structure which can be experienced within a short time due to smoke, heat and the fire fighting water. c. What is meant by Fire resistance? Fire resistance is defined as the that are laid down within a construction premise which are required by the building construction regulations that helps to withstand the damages that are likely to be caused within the building. These include such factors as resisting collapse and the excessive heat transfer within the building compartments. d. What is meant by Cavity barrier? Cavity barriers may be defined as the construction elements that are put in place and are meant to help restrict the rapid spread of flames and smoke through the cavities within a building premise. They are so vital in reducing the chances of unseen fire spread from one part of a building compartment to another. This reduces the damages within a premise. 17. Figure 1 and Figure 1(a) represents a two-storey office building, from the dimensions. Give an estimate for internal room sizes. With reference to Figures 1 and 1(a) determine: With reference to Figures 1 and 1(a) determine the travel distances from each room and each floor, Ground floor, 1st floor, and 2nd floor 1st rooms from exit is calculated as; =(5 m + 5 m) which results into a total travel distance of 10 m 2nd rooms from exit is calculated as; = 10 m + 5 m which results into a total travel distance of 15 m 3rd rooms from exit is calculated as; = 15 m + 5 m which results into a total travel distance of 20m 4th rooms from exit is calculated as; = 20m + 5 m which results into a total travel distance of 25 m 5th rooms from exit is calculated as; = 25 m + 5 which results into a total travel distance of 30 m a. Considering the Occupancy load Considering the occupancy load, the arrangement of this layout indicates business occupancy where the occupant load is generally 1 person per 100 square feet of the total floor area. b. Considering the Purpose group The recommended layout for the purpose group stands for purpose group 4, shop, and commercial. c. Considering the Exit and final exit widths Total floor area is calculated as shown below; = (25 x 10) which results into a total floor area of 250 m2 Therefore the Occupancy load is calculated as; = 1 person which is divided by 100 square feet =100 square feet equals to 9.2m2 =Substituting this in the above equation, we get; = 1 person/ 9.2m2 Therefore, the total number of occupants per floor translates to; = 250/9.2 resulting into 27 persons For all the floors it is calculated as; = (27 x 3) resulting into a total number of 81 persons Therefore, considering the ADB, the corresponding figures for the calculated variables shows that, the exit width equals to 1000 mm and final exit width is 1800 mm d. Stair widths equals to 1000 mm from the ADB 18. Classification of wall and ceiling linings Classification of walls and ceiling linings is majorly done with respect to the total area covered. When the area covered is less than 4m2, then it is considered a small room and when the total area covered is more than 4m2 then the place is considered large . References Top of Form BARRACLOUGH, S. (2008). Fire safety. Chicago, Ill, Heinemann Library. DRYSDALE, D. (1999). An introduction to fire dynamics. Chichester, Wiley. Top of Form GREAT BRITAIN. (2007). Approved document B. London, NBS/RIBA Publishing. Bottom of Form RAU, D. M. (2010). Fire safety. New York, Marshall Cavendish Benchmark. REDSICKER, D. R., & O'CONNOR, J. J. (1997). Practical fire and arson investigation. Boco Raton, CRC Press. Bottom of Form SULTAN, M. A., SEGUIN, Y. P., & LEROUX, P. (1998). Fire resistance tests on full-scale floor assemblies. [Ottawa], CHMC. Read More

The understated equations can be put into use to illustrate the effect of temperature on the flammability limits (Rau 2010). LFLT=LFL25*[1-(0.75/Hc)*(T-25)] UFLT=UFL25*[1+(0.75/Hc)*(T-25)] Where ; Ht = heat of combustion & T i=the test temperature. Flammable material temperature measured LFT calculated LFT measured UFL calculated UFL benzene 25.0 N/A 1.130 N/A 5.470 benzene 50.0 1.100 5.60 benzene 100.0 0.95 1.050 6.10 5.860 benzene 250.0 0.70 0.880 7.40 6.640 toluene 25.0 N/A 0.920 N/A 5.390 toluene 50.0 0.90 5.

50 toluene 100.0 0.80 0.860 5.80 5.720 Toluene The temperature effect on the lower & upper explosive limit of toluene is illustrated in the diagrams below. The graphs indicate that the experimentally established of the extremely established figures of higher explosive values in the temperature limits are above the figures determined by empirical equations. For the lower explosive range it can be viewed that calculated figures from equations are much below the values calculated by the experiment and are seen to lie outside the explosion range calculated from the measured figures.

Heat Release Rate Heat release rate measurements are most of the times seen by most people as a piece of data to gather. The single most vital variable in characterizing ‘flammability’ of the products and their eventual fire hazard. Examples of fire histories illustrate that even though the fire deaths are majorly caused by toxic gases, the rate at which heat is released is the major predictor of fire hazard. Conversely, the toxicity of the burning gases plays a less significant role. The delays in the ignition time, as can be measured by different Bunsen burner tests, also have only a lesser significant effect on the fire hazard.

Fire safety of a performance-based design is most of the times evaluated by use of deterministic analysis. In this type of analysis, a given number of representative fire scenarios, and the design fire scenarios, are analyzed then a quantitative description then follows. The assumed fire characteristics are termed as design fire, for example there is only a design fire in connection with every design fire scenario. A design fire in most occasions defined with respect to the heat release rate, toxic species available, and the rate of smoke production.

This report gives an exhaustive guidance in the selection of the design fires and it must be a vital resource for the fire protection personnel working with analyses that involve design fires. The report outlines a step-by-step operation method in which design fires are selected and outlines the factors that affect the design fire. Factors which Influence Fire Development & Rate of Fire Growth within A Compartment 1. Remote ignition This refers to the sudden ignition brought about by auto ignition or piloted ignition, contributed by the flaming brands, due to the radiant heating.

The radiant heating is primarily from the compartment ceiling and the hot upper gases because of their large extent. The required threshold for the piloted ignition of many materials is about 20 kW/m2. This value of flux, is measured at the floor, and is majorly taken as an operational criterion for the flashover. It equally relates to gas temperatures of 500–600 C. Phases of fire development 2. Rapid flame spread The radiant preheating of the material may the surface temperature of a material to move towards the piloted ignition temperature.

This may cause flammability limit to happen a head of the surface flame, which may cause a singularity in the simple flame theory hence causing a very rapid outcome, which may be in the order of 1m/s. 3. Burning instability Without fire spreading away from a burning item, the sudden fire eruption may be identified under the right conditions (Drysdale 1999). In this case, the thermal feedback that exists between heated compartment and the burning object may really cause a ‘jump’ from the initial stable state of the burning at the unheated, and the ambient conditions to the new stable state after the heating of compartment and the burning of the fuel come to the equilibrium. 4.

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