Wednesday, October 13, 2010

Fighting Fires - Several Stories Up

  • We're happy that Mrs. O-Leary's cow didn't start the Great Chicago Fire.
  • We're happy that Chicago was able to rebuild using modern technologies.
  • We're even happier to know that fire fighting methods continue to improve, especially when it comes to fighting blazes in multi-story apartment and office buildings.

The U.S. National Institute of Standards and Technology (NIST) has a Building and Fire Research Laboratory.  As you can imagine, this laboratory researches fires: how they start, how they propagate, how to prevent fires, how to fight fires, and most importantly fire safety.  (They have some really cool CFD tools to simulate fire.)  But, much like the Great Chicago Fire, "greatness" usually comes after a tragedy.

In December 1998, three New York City firefighters lost their lives due to thermal shock that was created when the windows of the apartment building they were securing failed and coincidentally an occupant of the apartment complex on the opposite side of the building opened a door.  The wind, from being several stories up, rushed through the open windows and carried the heat of the fire through the hallway in which the firefighters were traversing and down the open door.  The heat was so intense that the firefighters' bodies shut down; they had no time to escape.

This tragedy, like many others like it, have opened the eyes of researches in understanding more about the world around us and inspired new ways to keep people safe.  This is especially important in apartment fires.  The National Fire Protection Association stated that 7,300 high-rise fires occurred in 2002, mostly in residential buildings.  Of these, 92% of the fatalities occurred because the fire spread beyond the room of origin.  Something as simple as closing a door may have prevented those fatalities.

Developing New Methods
If a slight breeze can cause such devastation in a high-rise fire, how can it be limited?  Better yet, how can it be used to help stop the fire?

Simple, when a window is open, close it.  With a big curtain.

One of the main problems fighting a high-rise fire is getting water to the upper levels of the buildings.  Ladder trucks have nozzles, but they only reach a certain height.  Sending in firefighters is the usual option, but that exposes them to dangers that may result in the same tragedy that occurred in New York.  Therefore, a concept developed by New York and Chicago firefighters is the high-rise nozzle.
Firefighters can enter the building from a floor not exposed to fire or excessive heat and deploy a water nozzle to the floor above.

Smoke inhalation is the largest known contributor to fire deaths.  Smoke also happens to be the largest inhibitor to quick fire response due to the lack of visibility.  Chicago firefighters have begun testing large portable fans to create a positive pressure in stairwells and rooms.  This controls the smoke and heat of the fire, sometimes containing it to the room of origin.

(above images courtesy of of Governors Island Experiments)

Proving the Point
Ideas are great, but how do you prove they work?  You do so, by teaming up with NIST and the Polytechnic Institute by finding a little funding through the Department of Homeland Security, FEMA, the US Fire Administration, and the Assistance to Firefighters Research and Development Grant Program.

Using NIST's fire laboratory, quantitative measurements could be taken that showed improvements in temperature, heat flux, gas velocity, pressure, oxygen, carbon dioxide, and unburned hydrocarbons.  Seeing positive results in all of the experiments using the ideas devised by New York and Chicago firefighters, the testing move out of the lab and into controlled burns.

Abandoned Military Bases
Where else better to light a building on fire than an old building owned by the government that is no longer in use?  How about Governors Island, south of Manhattan, and home of an abandoned military base containing several multi-story buildings?

These experiments verified what the lab testing had shown.  Controlling wind - either by removing it in some areas or adding it in others (positive pressure) - significantly improved fire fighting conditions and also made it easier for occupants to egress from the building.  Several fire departments from North America were present to watch the experiments and are now looking at implementing them as standard practice.

And lets not forget that great software.  With empirical data under its belt, NIST can continue to develop a theoretical model to simulate fires using a combination of Fluent and NIST's Fire Dynamics Simulator.  As more simulations are run and the effectiveness of the new tactics proven, you can bet that new construction will see implementations of these techniques built right in.  The simulations also provide a great method to train firefighters on these new tactics and show them the positive and negative effects of using them.

Of course, the part that interests me the most about WHY these tactics need to be developed goes all the way back to the Great Chicago Fire.  When Chicago rebuilt with high-rises, the technology that we have available today, like deluge sprinklers, didn't exist.  So now, all of those older buildings need new, portable, ways to control fires.  Hopefully, with these new techniques, we don't have another Great Fire in any city.

For More Information
NIST Building and Fire Research Lab
Polytech Institute

1 comment:

  1. Very introspective. Where did you learn about this?

    Prof. Marvin May