Ventilation for Smoke Control, Fire Control & Life Safety in Tunnels. Dr. Ricky Carvel BRE Centre for Fire Safety Engineering University of Edinburgh

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2 Ventilation for Smoke Control, Fire Control & Life Safety in Tunnels Dr. Ricky Carvel BRE Centre for Fire Safety Engineering University of Edinburgh

3 Tunnel Ventilation? Tunnel ventilation was invented as a pollution control system Edge Hill railway tunnel, UK (1870) extract fan The Holland Tunnel, USA (1927) fully transverse The Queensway Tunnel, UK (1934) semi-transverse Bargagli-Ferriere Tunnel, Italy (1971) jet fans Why do we use it as a fire safety system? Is it a fire safety system?

4 What Happens When You Blow on a Fire?

5 What Happens When You Blow on a Fire?

6 What Happens When You Blow on a Fire? Backlayering

7 This Strategy Generally Works for Road Tunnels The strategy is to protect the queue

8 Does It Work for Rail Tunnels? Where is the queue we need to protect? Can the vehicles ahead just drive away?

9 What Should We Do with Ventilation Here? What would happen if we turned the ventilation system up? What would happen if we turned the ventilation system off? How would this affect the fire, the smoke, the people?

10 Ventilation vs. Smoke Good Bad Critical ventilation velocity Ventilation Smoke control

11 But Blowing on a fire doesn t just move the smoke. It also influences the fire dynamics! Do we care?

12 Ventilation vs. Fire Size Fire Enhancement Factor Critical ventilation velocity Ventilation velocity [m/s] Single lane tunnel Two lane tunnel See my PhD thesis or FSJ papers 2001 for details...

13 Ventilation vs. Fire Growth Heat Release Rate Time See paper in ISTSS 2008 or Handbook of Tunnel Fire Safety

14 Ventilation vs. Fire Growth Length of delay (min) Critical ventilation velocity Ventilation velocity [m/s] Delay phase See paper in ISTSS 2008 or Handbook of Tunnel Fire Safety

15 Ventilation vs. Fire Growth Growth rate (MW/min) Critical ventilation velocity Ventilation velocity [m/s] Growth phase See paper in ISTSS 2008 or Handbook of Tunnel Fire Safety

16 Ventilation vs. Fire Spread Probability of spread (%) Critical ventilation velocity Medium fire [32-64 MW] Ventilation velocity [m/s] Example data for two lane tunnel, 5 m vehicle separation. See paper in 4 th Int Conf Tunnel Fire Safety, 2004

17 Ventilation vs. Fire Good Bad Critical ventilation velocity Smoke control Delay duration Fire Spread Growth rate Peak Fire Size Ventilation So What Should We Do?

18 What should we do? That depends on one thing: How nasty is the smoke? For decades, fire strategies have been developed to keep smoke away from people and people away from smoke. Rarely have we stopped to ask questions about the properties of the smoke. Is smoke bad for you?

19 Which Smoke? If we blow on the fire, we get: Fast growing, large fire, that is reasonably well ventilated and we blow the smoke away from half (?) the people If we don t blow on the fire, we get: Slower growing, smaller fire, that is underventilated and we expose all (or most) of the people to smoke Which Is the Better Strategy?

20 How to Decide? There is really no one size fits all solution. This is what Performance-Based Design is all about. We studied the case of a typical, 18 carriage, modern, high-speed, inter-city passenger train, stopping due to fire in a tunnel with cross passages. (Disclaimer: Conclusions are not transferrable to other situations) (The problem with trying to show trains on screen is that they re just too long )

21 If the fire is on carriage 2: If the fire is on carriage 9: About 375m

22 Ventilation FED = 1 FED = 0.3 No forced ventilation

23 Ventilation FED = 1 FED = 0.3 No forced ventilation

24 So What Does This Mean? For this very specific scenario: If the fire is near the middle of the train: with natural ventilation, everyone escapes through tenable smoke with forced ventilation, half the passengers are completely fine, half may be exposed to problematic levels of smoke. If the fire is near the end of the train (but still with some people on both sides of it): with natural ventilation, everyone escapes through tenable smoke with forced ventilation, most of the passengers are completely fine, but the small number downstream of the fire are unlikely to survive! Do you know where the fire is? If in doubt, use natural ventilation!

25 Why? You can t divorce smoke control from fire dynamics!

26 An Introduction to Tunnel Fires Short Course Edinburgh, UK 5-6 September BRE Centre for Fire Safety Engineering