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  1. Wrightstyle
14 June 2009

Fire Safety and the House of Pain

Wrightstyle Limited is the UK’s leading supplier of integrated steel and glass systems with an international client base. Simon Bennett, the company’s international sales director, takes a look back at what was assessed as a routine domestic fire and which has lessons for everyone involved in residential or commercial building design.

They call it the House of Pain, and the fire fighters of Engine Company Ten and Truck Company 13 experience quite a lot of it. Theirs is the busiest fire station in the US, serving a large residential area of northeast Washington DC.

It gained its nickname in 1991, when fire crews were called out 9,947 times. Between 1991 and 2000, the House of Pain responded to 75,526 fires and other emergencies. In the first four months of this year alone, they logged 3,339 callouts.

Early on 30 May 1999 at 17 minutes past midnight, the District of Columbia Fire and Emergency Medical Services Communications Centre received a 911 telephone call reporting a fire at 3150 Cherry Road.

The residents of the property had been woken by their smoke alarm, gone downstairs to the first floor, and found smoke and heat. Wisely, they left the house through the front door, leaving the front door open.

In response, Communications dispatched four engine and two truck companies, a battalion fire chief and a rescue squad. A second 911 call less than two minutes later provided a corrected address of 3146 Cherry Road and reported that there was fire in the basement.

The first units were on the scene within four minutes of dispatch and at approximately 00:24 fire fighters began entering the first floor via the front door, through which was coming heavy smoke.

Among the fire fighters from Engines Ten and 26, the first to arrive on the scene, were Anthony Phillips and Louis Matthews, a 29-year-old divorced father who had celebrated his son’s second birthday only the week before. Matthews was a seven-year veteran of the fire service.

Within two minutes, the front window on the first floor was taken out by the fire fighters to provide additional ventilation. The window was removed from the inside, due to obstructions from security bars on the outside. Fire fighters also opened windows on the second storey at the front of the house.

Another fire team, positioned by sliding glass doors at the basement level, reported that the basement was full of smoke but that there seemed to be very little fire. Despite significant confusion over the exact location of the fire fighters upstairs, a decision was taken to break out the basement’s sliding glass.

This was achieved in two stages. First, the right half was taken out at approximately 00:26. Then the left side was removed approximately 20 seconds later. Once again, there were obstructions from security bars. After the sliding glass door was broken out, fire fighters entered the basement to conduct a search.

They reported that there were a number of small fires on the floor of the basement. However, these rapidly increased in size after the sliding glass door was opened. The fire fighters were ordered out of the basement as the fire quickly intensified.

Luckily, the team saw a tunnel through the smoke and it was that safe pathway that allowed them to find their way out of the basement, just before it became engulfed in a fully-fledged inferno. Seconds later, from upstairs, came the first report of a fire fighter down.

It was worse. District of Columbia Fire Fighter Anthony Phillips was pronounced dead on arrival at hospital, becoming the 96th fire fighter to die in the line of duty. F/F Louis Mathews, the 97th, died the following day as a result of his injuries, the first double line-of-duty deaths in almost 90 years for the city’s fire service.

Two other fire fighters sustained minor injuries but a third, Fire Sergeant Joe Morgan, 36, also from Engine 26, spent 180 days in hospital and underwent over 21 surgical procedures for 60% burns. On admission, the father of four was given only a 5% chance of survival and one doctor described his recovery as a miracle. Joe Morgan returned to work as an instructor, never again as a front-line fire fighter, but soon afterwards was forced to retire because of disability.

It was the very routine nature of the fire and its tragic outcome that prompted the District of Columbia Fire and Emergency Medical Services Department Reconstruction Committee to request a full investigation into the fire dynamics of the incident.

This was carried out by the Building and Fire Research Laboratory (BFRL) at the National Institute of Standards and Technology (NIST), whose mission is to conduct basic and applied fire research, including fire investigations, for the purposes of understanding fundamental fire behaviour and to reduce loss of life.

The investigation made use of the NIST Fire Dynamics Simulator (FDS), a computer modelling programme that looked at data from three sources: the District of Columbia Fire and Emergency Medical Services Department Reconstruction Committee, photographs and measurements taken by NIST staff, and from material properties taken from the FDS database.

The investigating team wanted to know how the opening of windows and doors had affected the dynamics of the fire. By using sophisticated modelling techniques, the investigators were able to run different scenarios and see the different computer predictions. They could then match what the simulator showed with information they had collected from the scene and from witnesses.

Next, investigators identified what is referred to as the fuel package or fuel load that was involved in the fire, the total quantity of combustible contents of the space. NIST’s simulator was then plugged into a database of the heat release rates of different types of furniture and furnishings, expressed as British Thermal Units (BTUs) or Kilowatts (kW) per second.

The model divides the space involved in the fire into thousands of “cells”. In the Cherry Road simulations, the cells measured just eight inches by four inches high. Once the physical data was entered into the computer, it was able to model the conditions for each cell and then combine all of them together to provide an overall simulation of the fire.

Investigators determined that the fire started near an electrical fixture in the ceiling of the basement, and that the actual fire may have taken several hours to develop to a flaming stage. As the fire spread from the ignition source, first along the ceiling and then to other items in the basement, it developed quickly at first but then depleted the supply of oxygen necessary for combustion.

This lack of oxygen had the effect of rapidly decreasing the heat release rate or energy being produced by the fire. It was at this point, when the fire’s heat release rate was being constrained, that fire fighters made their entry on the first floor of the building. However, and against some expectations, opening windows on the front of the townhouse on the first and second floors seemed to have had no noticeable impact on the fire development.

It was the breaking open of the basement door that created the firestorm. The FDS calculations were that the opening of the basement sliding glass doors provided outside air into a pre-heated but under ventilated fire compartment, which then developed into a post-flashover fire within 60 seconds.

Some of the resulting fire gases flowed up the basement stairwell with a high velocity and collected in a pre-heated, oxygen depleted first floor living room with limited ventilation. More precisely, the model showed that the superheated gases moved up the stairs at approximately 18 miles per hour.

As the townhouse was only 33 feet high, it meant that the extremely hot gases moved through the townhouse in less than two seconds. F/F Anthony Phillips’ autopsy revealed that he died of “asphyxiation due to inhalation of superheated air, soot, and smoke”. In some respects, it was remarkable that the loss of life wasn’t greater.

What makes the Cherry Road fire so important is that it was a catastrophic fire that took place in a relatively small area so that its fire dynamics were capable of analysis, using techniques at the forefront of forensic science. Two facts were immediately clear. First, it underlined how a relatively insignificant fire can become an inferno in a matter of seconds and that, when it does, flashover can engulf a whole building in a few moments. Second, the inferno was caused by breaking open the compartment within which the fire was contained. Many of the lessons of the Cherry Road fire are now part of US fire training programmes.

This is at the heart of compartmentation and is what Wrightstyle glass and framing systems are there to do: provide effective barriers against the passage of fire, heat and toxic gas and, by preventing oxygen from reaching the seat of the fire, inhibiting its progress. This allows people to escape and, by containing the fire, minimises fire damage.

Every year, fire kills an estimated 166,000 people worldwide – that’s nearly 19 fatalities every hour of every day. Some estimates suggest nearly 300,000 deaths per year. The International Technical Committee for the Prevention and Extinction of Fire (CTIF) estimates that the annual cost of fire damage adds up to a whopping 1% of international GDP or €400 billion.

The main lesson for today’s designers is not simply to build in passive and active fire systems, but to look at the whole building’s capacity to withstand a fire situation. For the glazed components, that should mean analysing the level of containment the glass will provide and its compatibility with its framing systems.

In many instances, untested combinations of glass and frame are specified separately – despite the fact that in a fire situation the glass will only be as good as its framing system, and vice versa. Insisting on tested, and therefore proven, compatibility, and specifying it as a requirement of the tendering process should be a matter of course.

As the Cherry Road fire showed, failure to contain fire can have very human consequences, even in a residential home. In larger multi-storey buildings the stakes are very much higher and the responsibility on the designer that much greater.

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