Annual Fire Safety Engineering Conference 2013
A DECADE OF SCANDINAVIAN RESEARCH AIMED AT BENEFITING THE FIRE SERVICE
Dr. Björn Karlsson Arnheim, 12-13 November 2013
Dr. Björn Karlsson 1 CV, Dr. Björn Karlsson
• B.Sc. Civ Eng, Heriot-Watt University, Edinburgh, 1985 • Ph.D. in Fire Safety and Risk Engineering, Lund University, Sweden, 1992 • Associate Professor at Lund University, 1992-2001 • Associate Professor, Civ. Eng. Dept., University of Iceland, 2006- • Director General of the Iceland Fire Authority 2001- 2010 • Director General of the Iceland Construction Authority • In charge of Fire safety, Electrical safety and Building Regulations, also control the Fire Service College
Dr. Björn Karlsson 2 Contents
• Background • Flashover, backdraft, smoke gas explosion • Ventilation • Suppression • Tactics • Conclusions
Dr. Björn Karlsson 3 Background
• Fire fighter training and experience is important, but buildings are getting much more complex (atria, underground, etc) • Rapid progress in understanding fire phenomena, computer programs, etc • Important to use new technology in training • Here: Give overview of research for fire service, researchers from Lund University who subsequently worked in fire service
Dr. Björn Karlsson 4 Flashover, backdraft, smoke gas explosion
• Very hazardous phenomena • Controversy over terms used – Flameover, rollover, lean and rich flashover, etc • Research project with aims to – Clarify terminology – Increase understanding of the dominant thermal and chemical processes – Produce basis for teaching material
Dr. Björn Karlsson 5 Flashover, backdraft, smoke gas explosion
Temp
Flashover
Growht to flashover
Backdraft Tid
Dr. Björn Karlsson 6 Motivation for training Fire Fighters
• Fire fighters face dangerous situations – Must understand the chemical and physical processes involved – Must understand the warning signs – Must know how to deal with these problems • A compartment fire can develop in many different ways, not all are hazardous
Dr. Björn Karlsson 7 Fire development in well ventilated spaces • Well ventilated fire without spread to other item – A very common situation – Easy to deal with • Well ventilated fires leading to Flashover – Occurs in about 5-10% of all building fires – The warning signs are important
Dr. Björn Karlsson 8 Flashover, “A sudden event”
Extinguishment 1000 900 800 Temp 7 700 Temp 8
) 600 Flashover
C Temp 9
°
( 500 Temp 10 T 400 300 Temp 11 200 Temp 12 100 0 0 200 400 600 800 Time (s)
Dr. Björn Karlsson 9 Warning signs of a potential flashover
• Increasing speed of the gases leaving the room • Neutral layer moves towards the floor • The colour of the smoke? – Very much depending on the material burning
Dr. Björn Karlsson 10 Fire development in poorly ventilated spaces
Temp Fully developed fire
Flashover B
Lack of oxygen A
Time
Dr. Björn Karlsson 11 Fire development in poorly ventilated spaces
• Four common
Temp Fully developed fire outcomes: – Self-extinction
Flashover B – Auto-ignition of gases
Lack of oxygen – Flashover A – Backdraft
Time
Dr. Björn Karlsson 12 Self-extinction
• Very common • Easy to deal with • Can still create dangerous conditions for the people inside the building
Dr. Björn Karlsson 13 Auto ignition of the gases
Temp Auto ignition
Flashover
Growth to flashover
Lack of oxygen Tid
Dr. Björn Karlsson 14 Growth to Flashover
Temp
Flashover
Growht to flashover
Backdraft Tid
Dr. Björn Karlsson 15 Backdraft
• The most hazardous situation • Conditions favourable for backdraft are – Well isolated room – Fuel is placed in the upper part – A smouldering fire that has been ongoing for a long time
Dr. Björn Karlsson 16 Occurrence and mitigation of backdraft • Frequency – How often does the phenomena occur? • Warning signs of a potential backdraft – The colour of the smoke? • A new method for mitigating backdraft – The cutting extinguisher
Dr. Björn Karlsson 17 Warning signs of a potential backdraft
• The fire may be pulsating • No visible flame in the fire room • Whistling sounds around doors and windows • If the fire has been burning for a long time in a concealed space, a lot of unburned gases may have accumulated • Hot doors and windows
Dr. Björn Karlsson 18 Smoke gas explosion
• Definition – When smoke gases are transported into an enclosure adjacent to the fire compartment, these can mix well with fresh air. This mixture can spread through parts of, or the entire volume of the enclosure and its concentration be within the flammability limits of the mixture. If the mixture ignites the increase in pressure may be extremely high. This is called a smoke gas explosion
Dr. Björn Karlsson 19 Warning signs of a potential smoke gas explosion? • Is the construction well sealed? • Does the building construction contain hidden spaces? • Are the building elements themselves combustible? • Are there any unsealed penetrations leading from the fire compartment, such as ventilation ducts?
Dr. Björn Karlsson 20 The Grey Zone
Fire Development
Temp
The grey zone
Flashover Growth to flashover
Backdraught
Time
Dr. Björn Karlsson 21 Results
• The phenomena Flashover, Backdraft and Smoke gas explosion occur relatively seldom but can involve great danger to fire fighters • The work divides potentially hazardous situations into categories based on fundamental physical and chemical processes • These categories are observed in practice and experiments have been performed for verification • The phenomena are closely related and it can in some cases be difficult to distinguish one from the other
Dr. Björn Karlsson 22 Result
A new textbook for Fire Fighters And Fire Officers used by the Swedish Fire and Rescue Training Facilities
Dr. Björn Karlsson 23 Backdraft
• Backdraft arises from an under-ventilated fire • A majority of fires are under-ventilated, or limited to first item ignited, when the fire service arrives on the scene • Most fire research work over the last 40 years has concentrated on well-ventilated fires • In under-ventilated fires one must deal with both thermal and chemical processes • Our aim: Educational material for fire fighters
Dr. Björn Karlsson 24 Dr. Björn Karlsson 25 Dr. Björn Karlsson 26 Experimental apparatus: Backdraft
Dr. Björn Karlsson 27 Salt water modelling
Dr. Björn Karlsson 28 Dr. Björn Karlsson 29 Risk of Backdraft vs Tactics
Dr. Björn Karlsson 30 Risk of Backdraft vs Tactics
Four situations studied 1. Offensive attack, BA team enters front door 2. Defensive attack, natural ventilation by opening a window at the back 3. PPV at high flow rate 5.38 m3/s. 4. Incorrect use of PPV at 5.38 m3/s, but closed outlet window at the back
Dr. Björn Karlsson 31 Risk of Backdraft vs Tactics
Dr. Björn Karlsson 32 1. Offensive attack
• People left inside the compartment • Time is a critical factor • BA team will enter through the front door and cool the hot gases 1. Offensive attack
Gravity current speed : 1-2 m/s, a flammable region is created in only a few seconds 2. Defensive attack, natural ventilation
• Compartment evacuated • Time not as critical as in Scenario 1 • No unnecessary risks are taken • There are enough resources to perform the ventilation 2. Defensive attack, natural ventilation Dangerous conditions are reached fast, the compartment is more quickly vented, demands resources, protecting facade 3. Offensive attack, PPV
• Using PPV at an early stage of an operation is getting more common • Sometimes used in life-saving operations • Recommendation: ”Use with great caution” • Resources needed at discharge opening 3. Offensive attack, PPV Effective way of clearing the compartment of fire gases, increased mixing for a very short period, discharge opening must be protected with water 4. Incorrect use of PPV
•What happens if the discharge opening is blocked ? •Scenario 4 simulated without the discharge opening 4. Incorrect use of PPV Explosive mixture collects more at ceiling level, smoke can be forced, due to the overpressure, into areas not yet damaged by the smoke Contents
• Background • Flashover, backdraft, smoke gas explosion • Ventilation • Suppression • Tactics • Conclusions
Dr. Björn Karlsson 41 Ventilation
1. Experimental Study of Fire Ventilation Actions During Firefighting Operations 2. Experimental Study of Fire Ventilation Procedures in a Large Hall 3. Investigating positive pressure ventilation (see Presentation A-2)
Dr. Björn Karlsson 42 1. Study of fire ventilation during fire fighting operations
• Purpose of the tests – investigate the effect of measures taken by fire & rescue services, including positive pressure ventilation – to provide fire & rescue services with qualitative data to be used as a basis for decision making on the fire ground – 15 experiments • Experimental set-up – fire fighter training facility (concrete/lightweight concrete) – 0.50 m diameter heptane pool, burn time app. 700 seconds, RHR appr. 0.37 MW – PPV by a Typhoon 18T5 fan, nominal flow of 2.7 m3/s
Dr. Björn Karlsson 43 The test facility
Dr. Björn Karlsson 44 Experimental lay-out
Dr. Björn Karlsson 45 Fire fighting scenarios
A. via staircase (access route through D4, Room 4, D3), window (W) closed B. via window (W), door between staircase (Room 4) and apartment closed (D3) C. via staircase (access route through D4, Room 4, D3), window (W) open D. via staircase (access route through D4, Room 4, D3), window (W) open, PPV, fan positioned in Room 4 E. via staircase (access route through D4, Room 4, D3), window (W) open, PPV, fan positioned outside door to staircase (D4)
Dr. Björn Karlsson 46 2. Study of fire ventilation procedures in a large hall
• Purpose of the tests – Investigate fire ventilation actions taken by the fire services, including PPV, for fires in large halls • Experimental set-up – Five tests were performed in a large hall measuring 39 m long, 11.2 m wide and 8.1 m in ceiling height – 12 m methanol pool, RHR appr. 1.0 MW – Smoke was produced using propylene glycol from smoke generators – PPV provided by a standard type fan, nominal flow of 4.5 m3/s.
Dr. Björn Karlsson 47 Experimental lay-out
All dimensions in meter [m] 6.5 3.25 9.75 9.75 3.25 6.5
3.0 C1 C2 P1 – P3 T5 D1 Position of fan in test 1 - 4 T6 T2 Centerline T1 T3 T4 L 11.2 Position of fire, 2m2 P6 P4 P5 W1 W2 D2 3.0 Position of fan Experimental set-up: in test 5 T1 – T6 stacks of thermocouples C1 – C2 video camera P1 – P6 flow probes L Load cell North W1 – W2 windows, 3.3 0.6 m (soffit 0.4 m below ceiling) D1 - D2 doors, 1 2 m Dr. Björn Karlsson 48 Investigated scenarios
1. Door in the south wall, D1 2. Window at ceiling level in the northeast corner, W1 3. Door in the south wall, D1 in figure 1, and window at ceiling level in the northeast corner, W1 4. Door in the south wall, D1, and window at ceiling level in the northeast corner, W1, using positive pressure ventilation, fan located approximately 3 m outside D1, blowing into the hall 5. Door in the northeast corner, D2, and window at ceiling level in the southeast corner, W2, using positive pressure ventilation, fan located approximately 3 m outside D2, blowing into the hall
Dr. Björn Karlsson 49 3. Investigating positive pressure ventilation
• Purpose of the tests – effects of distance between fan and inlet – size and numbers of outlets – volume of building • Experimental set-up – Forty-three experiments on the first, second, and third floors of a three-storey brick building with wooden trusses – Cold-flow only (unfortunately…)
Dr. Björn Karlsson 50 The test facility
Dr. Björn Karlsson 51 Results
• Including comparison with CFD-calculations
Dr. Björn Karlsson 52 Results • Positive pressure ventilation increases the mass loss rate of fuel, consequently increasing burning rate of the fire, also, risk of fire spread to adjacent rooms will increase • Working conditions for fire fighters are improved by positive pressure ventilation, but the lives of any victims trapped in an apartment on fire are jeopardised • Co-ordination of different measures at a fire scene is crucial and the importance of command and control is prominent. • Exhaust flow rate decreases as volume of the structure increases
Dr. Björn Karlsson 53 Result
A new textbook for Fire Fighters And Fire Officers used by the Swedish Fire and Rescue Training Facilities
Dr. Björn Karlsson 54 Contents
• Background • Flashover, backdraft, smoke gas explosion • Ventilation • Suppression • Tactics • Conclusions
Dr. Björn Karlsson 55 Suppression
1. Live Fire Tests on Suppression of Post- flashover Fires using Manually Applied High and Low Pressure Water Sprays 2. Fire Tests in a Large Hall, using manually Applied high and Low Pressure Water Sprays
Dr. Björn Karlsson 56 1. Suppression Tests Using High and Low Pressure Water Sprays
• Purpose of the tests – Compare a high-pressure (40 bar) system with a normal pressure (10 bar) system, systems mounted on a fire engine • Experimental set-up – 15 tests in a fire fighter training facility – Water application using a manually oscillated nozzle – Actual fire-fighting techniques – The fuel was applied on the walls and in the ceiling of a fire fighting training facility, appr. 18 m2, 18-mm particleboard
Dr. Björn Karlsson 57 The test facility
18 thermocouples at heights 1 m and 2 m above floor, located opening at 0.1 m, 2.5 m and 7.5 m from far end wall, respectively. 2.5 1.1 m
2.5 m
5 m 12 m = thermocouple
Dr. Björn Karlsson 58 2. Tests In A Large Hall, High- And Low Pressure Water Sprays
• Purpose of the tests – investigate the capacity of the fire service to fight fires in large spaces and obtain quantitative data – compare a high-pressure with a low-pressure system – measure the heat stress on BA-equipped fire fighters • Experimental set-up – Six tests in a room measuring 14.0 7.7 m², 6.3 m in height, with 0.4 m thick walls of concrete – The fuel consisted of standard wood pallets arranged in 6 stacks with 13 pallet in each stack
Dr. Björn Karlsson 59 The test facility
Dr. Björn Karlsson 60 The test facility
T2
1.88 2.10 2.00 2.00
3.53 3.05 2.85 3.06 0.91 L2 L3 T3 T4 T5 T1
Point of attack Attack route of 4.05 X BA-equipped fire fighters K2 S2 0.30 2.25 S1 0.90 2.70 3.20 0.98 L1 T8 T9 T10 T6 1.78 2.10 2.10 2.10 P1 K1 0.70 T7 0.73 1.48 0.0 1.0 5.0 10.0 All dimensions in m F1 0.80 Pallets used Experimental set-up: in the tests 1.20 F1 Flow meter P1 Pressure gauge K1-K2 Video cameras S1-S2 Radiometers 0.14 L1-L3 Load cells T1-T10 Stacks of thermocouples
Dr. Björn Karlsson 61 Results • A rigid hose used together with a high-pressure system generally decreases the attack time and reduces temperatures quicker • High-pressure system has a better extinguishing effect regarding gas phase extinction • When both surface cooling effects and gas phase effects are considered, the high-pressure system requires only 2/3 of the water required by the low-pressure system to achieve the same extinction capacity in this scenario • The increase in fire fighter pulse rate appeared to be triggered by stress and increased due to increasing skin
temperature Dr. Björn Karlsson 62 Results
A new textbook for Fire Fighters And Fire Officers used by the Swedish Fire and Rescue Training Facilities
Dr. Björn Karlsson 63 Contents
• Background • Flashover, backdraft, smoke gas explosion • Ventilation • Suppression • Tactics • Conclusions
Dr. Björn Karlsson 64 Tactics
1. A Study of Tactical Patterns During Firefighting Operations 2. Investigating Firefighting Tactics in a Mechanical Workshop 3. Investigating Tactical Patterns in a Residential Type Structure 4. Tactical Patterns and Their Implications for Fire Fighting Operations
Dr. Björn Karlsson 65 1. Tactical Patterns During Firefighting Operations
• Purpose of the tests – to investigate how tactical patterns interact with a fire in an apartment – examine and draw conclusions from the course of events during operations and on their outcomes – a basis for further treatment of command and control problems • Experimental set-up – twenty tests performed in a fire fighter training facility – eight standard wooden pallets used as fuel in each test
Dr. Björn Karlsson 66 Questions of interest
• Why is a specific task chosen during a fire fighting operation? • What happens when this task is executed? • What would have happened if some other task were to be executed? • What would have happened if the task were to be executed at some other point in time or space?
Dr. Björn Karlsson 67 The basic idea
Available X Y procedures Possible only first X X and combinations X then Y Y only first Y Dr. BjörnY Karlsson then X 68 The test facility
Dr. Björn Karlsson 69 Experimental lay-out
Position of fan H1 (at ground level) C Attack route and 1.5 position of fire fighter
D2 D4 Position of fire in tests 1 - 5 T1 T2, P T3 T4 5.0 2.6 W Centerline Position of fire D3 (on platform) 0.5 0.5 0.5 1.4 Room 4 L2 L1 1.0 D1 L3 Room 1 Room 2 Room 3 H2 2.8 3.4 1.8 5.7
All dimensions in meter [m] Experimental set-up: T1 - T4 stacks of thermocouples P pressure gauge L1 – L3 load cells C camera ("Hubert") 2 W window, 0.88 1.18 m 2 D1 - D2 doors, 1.16 1.98 m 2 D3 - D4 doors, 0.92 2.00 m 2 H1 - H2 hatches, 0.6 0.2 m
Dr. Björn Karlsson 70 Overview of tests
Test # Tactical pattern 1 Attack through the door to the apartment (D3), door to the apartment (D3) and window (W) opened. 2 Attack through the door to the apartment (D3), door to the apartment (D3) and window (W) opened, using positive pressure ventilation. 3 Attack through the door to the apartment (D3), door to the apartment (D3) and window (W) opened, using positive pressure ventilation. 4 Attack through the door to the apartment (D3), using positive pressure ventilation. 5 Attack through the door to the apartment (D3), door to the apartment (D3) and window (W) opened. 6 Attack through the window (W). 7 Attack through the window (W). 8 Attack through the door to the apartment (D3), door to the apartment (D3) and window (W) opened. 9 Attack through the door to the apartment (D3), door to the apartment (D3) and window (W) opened, using positive pressure ventilation. 10 Attack through the door to the apartment (D3), door to the apartment (D3) and window (W) opened, using positive pressure ventilation. 11 No attack (full-burn), door (D3) and window (W) opened and fire extinguished for safety reasons. 12 Attack through the door to the apartment (D3). 13 Attack through the door to the apartment (D3), door to the apartment (D3) and window (W) opened. 14 Attack through the door to the apartment (D3), door to the apartment (D3) and window (W) opened, using positive pressure ventilation. 15 Attack through the door to the apartment (D3), using positive pressure ventilation. 16 Attack through the door to the apartment (D3). 17 Attack through the door to the apartment (D3), door to the apartment (D3) and window (W) opened, using positive pressure ventilation. 18 Attack through the door to the apartment (D3), door to the apartment (D3) and window (W) opened. 19 Attack through the door to the apartment (D3), using positiveDr. Björn pressure Karlsson ventilation. 71 20 No attack (full-burn), door (D3) and window (W) opened and fire extinguished for safety reasons. Results
450 2.25 m above floor 1.59 m above floor 400 0.92 m above floor 0.25 m above floor 350
300
250
200
temperature [°C] 150
100
50
0 0 100 200 300 400 500 600 Test 9, room 2 time from fire start [s]
Dr. Björn Karlsson 72 Results
0,10 lower layer mean temperature in room 1 0,09 upper layer mean temperature in room 1 lower layer mean temperature in room 2 0,08 ] upper layer mean temperature in room 2
0,07 lower layer mean temperature in room 3
or
upper layer mean temperature in room 3 0,06 mean frequency 0,05
0,04
0,03
0,02
0,01
0,00
Frequency at end of operation [ -0,01
-0,02
-0,03
7 ; W+F
12 ; D+F
17 ; 10 ;
1 ; W/D+F 8 ; W/D+F
5 ; D+F+W
6 ; W+1.3F
16 ; D+0,5F
13 ; W+D+F
15 ; D/PPV+F
18 ; W+D+0,5F
9 ; W/D/PPV+F 2 ; W/D/PPV+F 3 ; W/D/PPV+F
4 ; D/PPV+1.3F
W+D/PPV+0,5F D/PPV+0,5F+W
19 ; D/PPV+0,5F
14 ; W+D/PPV+F Test # ; tactical pattern
Dr. Björn Karlsson 73 2. Fire Fighting Tactics in a Mechanical Workshop
• Purpose of the tests – verify basic tactical principles identified in earlier experiments – Verify the methodology for analysis • Experimental set-up – nine tests were performed in a fire fighting training facility, representing a small mechanical workshop – thirteen standard wooden pallets were used as fuel in each test
Dr. Björn Karlsson 74 Experimental lay-out
W1 Room 4
Experimental set-up: thermocouples L1 – L3 load cells W1 window (at ceiling level), W2 1.0 0.5 m2 11.8 W2 window (at floor level), 0.7 0.7 m2 2 L2 D1 – D3 doors, 0.8 2.0 m L1 C camera ("Hubert") L3 Room 5 Room 3 (upper) Position of fire (on platform)
Room 1 D2 D3 C Room 3 (lower) Room 2 D1
13.4 Position of fan Dr. Björn Karlsson 75 3. Tactical Patterns In A Residential Type Structure
• Purpose of the tests – verify basic tactical principles – verify the methodology of analysis – retrieve data for future work • Experimental set-up – 44 tests were performed in a residential type, multi-room fire fighter training facility – included various suppression techniques, positive pressure ventilation and various openings for ventilation – 10 wooden pallets were used as fuel in each test
Dr. Björn Karlsson 76 Experimental lay-out
Dr. Björn Karlsson 77 4. Tactics and their Implications for Fire Fighting Operations
Dr. Björn Karlsson 78 Results
• Fire fighting tactics can be experimentally investigated. Through such experiments basic tactical principals have been identified and verified. • In a wider perspective, the experiments constitute a basis for further treatment of command and control problems. • Based on this type of analysis, mathematical models for fire fighting operations can be developed.
Dr. Björn Karlsson 79 Basic tactical principals
• the outcome of a fire fighting operation is dependent on the individual procedures as well as on their sequence of implementation • the choice of tactical pattern is dependent on the situation as well as on the objectives of the fire fighting operation • various procedures initiated on the fire ground must be coordinated, i.e. command and control of fire fighting operations is vital • the choice of tactical patterns may be of a greater importance to the outcome of an operation than the outcome of a single procedure itself • certain tactical patterns have an inherent indulgence towards defective or inappropriate procedures • defective or inappropriate procedures or tactical patterns can be corrected during a fire fighting operation • an objective may change during a fire fighting operation and different objectives during an operation may influence what tactical patterns are considered as “correct” and what are considered as “incorrect”
Dr. Björn Karlsson 80 Result
A new textbook for Fire Fighters And Fire Officers used by the Swedish Fire and Rescue Training Facilities
Dr. Björn Karlsson 81 Contents
• Background • Flashover, backdraft, smoke gas explosion • Ventilation, including PPV • Suppression • Tactics • Conclusions
Dr. Björn Karlsson 82 Conclusions
• Buildings getting much more complex (high atria, underground, etc) • Rapid progress in understanding fire phenomena, computer programs, etc • Important to facilitate rapid transfer of technology from fire science to the fire service • We do this by cooperating with fire service and training establishments, conducting experiments, and providing relevant and appropriate teaching material, with a sound scientific basis, to fire fighters and fire officers
Dr. Björn Karlsson 83 Educational material for fire fighters and fire officers
Dr. Björn Karlsson 84