The city is still grieving over the two firefighters who lost their lives in the line of duty, Senior Station Officer Thomas Cheung and Senior Fireman Samuel Hui.
Condolences continue to pour in for the families the two heroes left behind.
We are now also seeing the political repercussions of the tragedy at Amoycan Industrial Centre in Kowloon Bay.
Comrades-in-arms of the fallen firefighters and the public are questioning if there was any fault by the commander at the scene, if the top SAR officials, including Chief Executive Leung Chun-ying, meddled in the firefighting process, and if the Fire Services Department was under undue pressure to put down the fire, even at the cost of the safety of firefighters.
The best way to remember the two brave firemen is perhaps by promoting public awareness of fire safety, which in turn will help save lives.
ABCs of firefighting
In 2006 I attended a professional training in ocean sailing in the United Kingdom and the qualification test by the British Maritime and Coastguard Agency consisted of fire safety theories and a drill at the FireAid Academy’s training facilities in Southampton.
In a simulated fire, two trainees in full firefighting gear and carrying breathing apparatus were required to climb the stairs to reach a chamber filled with smoke to search for “victims”, and then extinguish the fire with pressurized fire hose reels.
The firefighting theory starts with the fire triangle: fuel, heat and oxygen are the necessary ingredients for most fires.
One thing to note is that even if there is little oxygen in the atmosphere, a fire can ignite and keep on burning as long as there are some oxygenated chemical compounds, like hydrogen peroxide, that can supply oxygen under certain circumstances.
There were oxygenated materials kept in many small, locked spaces at mini-storage facilities inside the Kowloon Bay building. Otherwise, the inferno, which lasted for 108 hours, would have died by itself once the oxygen inside those small cubicles was consumed.
Temperature at a fire scene may be between 600 and 1,000 degrees Celsius, but the protective clothing for firefighters can only function for a few minutes when exposed to a heat of 200 degrees.
Smoke more fatal than fire
The biggest threat at a fire scene is not fire but smoke generated by incomplete combustion, and other than causing suffocation, smoke is also flammable itself and can fuel the fire – the darker the color of the smoke, the more dangerous it is.
Flammable smoke can spread instantly, causing potential “flashover” and “backdraught” when there is enough oxygen – two of the most-feared phenomena among firefighters, and it is particularly so as people trapped may subconsciously follow the flow of smoke to flee the fire.
Tactical ventilation and flow path
Firefighters may have to deploy tactical ventilation to break into a tiny space or staircase filled with smoke, yet the practice is highly risky as changing flow path may lead to dire chain effects.
The concept of flow path of atmosphere, smoke and fire is one of the new firefighting theories.
If a fire breaks out in a confined room, it may go out after consuming all the oxygen inside, but if a window is open, then two-way convective flows – fresh, cool atmosphere coming in from the bottom and smoke flowing out from the top – will sustain the fire, and this is a dangerous scenario as smoke with temperature of 1,000 degrees may permeate the room due to slow convection, fueling the fire further.
If there is a new opening, like when the door is broken open, the blaze will only get stronger with more supply of oxygen and the extremely hot smoke may also pour out from the door, igniting almost anything along the way and even firefighters in their protective clothing may be severely hurt.
This explains why fireproof doors on different floors must be kept closed at all times, as otherwise the staircase or corridor may become a perfect passage for air and smoke flow, causing greater damage.
That’s also why after breaking into a fire scene, firefighters should seal the place again. One way is by closing the door or windows.
Once air blowers are turned on for tactical ventilation, firefighters must simultaneously douse the fire, otherwise more oxygen will only let the flames get out of control.
Thus, I have reasons to doubt if it is safe to open all windows for ventilation if caught inside a burning room, as advised by the Hong Kong Red Cross.
No surefire way in firefighting
Many suspect poorly orchestrated tactical ventilation may be responsible for the death of Senior Station Officer Cheung, after he was found unconscious inside the building.
It may be that he was caught by a sudden rise in temperature and smoke after follow-up actions were not done simultaneously with the turning on of the air blowers.
But don’t rush to blame the on-site commander.
In firefighting, an ex-ante decision can hardly be a surefire way since the actual condition is always overwhelmingly unpredictable.
The outcome of firefighting is determined by a plethora of factors including strategy, personnel deployment, equipment, building structure and design, and even the flammability of items at a fire scene.
This article appeared in the Hong Kong Economic Journal on June 27.
Translation by Frank Chen
[Chinese version 中文版]
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