Reflection on “Fire Risk at Your Home”

By LEE Chung Yan Daniel, St Paul’s College

“Fuel + Oxygen + Heat……” As one has heard in his science lessons, these are the components to start a fire. The above oxidation process releases heat and gives out light, sound, and products in the form of smoke.

Prof. Lee’s lecture kicked off by saying fire is a double-edged sword. Fire has been a significant part of our history and daily lives, from steam locomotives to lighting candles to cooking a meal. However, it can as well be the assassin to our memories, properties, and wildlife with fire accidents.

A statistic report from Fire Service Department in 2021 was shown in the lecture, highlighting that most of the fires reported throughout the year happened in domestic buildings and housing estates. Nowadays, interior designers proposed to renovate the protected kitchen to open kitchen for a more spacious area, ignoring the fact that hot gases may easily migrate to other areas while the radiation may also ignite other combustible items such as papers and cleaning products in the household. Residents living in sub-divided flats in HK do have to be more aware of the possible fire outbreaks in the kitchen, don’t they?

Prof. Lee also gave a detailed explanation of the fire dynamics and its physical concepts, which I found intriguing as it did explain some of the scenes filmed in some foreign fire television series. A fire has its growing stages, just like humans. As the fire plume emits radiation and heat, convections are formed since a cold layer of air from the surroundings moves in. The heated gas rises to the ceiling, gradually forming a thermal interface. Therefore, we should crawl on the ground during a fire to prevent the inhalation of toxic gases. A fire is said to be at its peak when it reaches the flashover period, equivalent to 600°C. A property can only be ventilated when the firefighters had completed their rescue since the temperature inside will abruptly rise to the flashover point upon contact with abundant oxygen supply from the outdoors.

Finally, Prof. Lee explained to us the timeline approach for fire safety assessment. The Required Safe Escape Time could be divided into detection time, alarm time, pre-movement time and evacuation time for calculations. Calculations could be made on a computer by computational fluid dynamics and simulations of the victim’s response time, average walking speed, evacuation routes, etc. Upon addition of a margin of safety, an Available Safe Escape Time, measuring the period from fire ignition to untenable condition (i.e. when the visibility is under 10m / temp.>65°C / CO concentration >1400ppm) could be determined for fire safety assessment. I think that these scales can be very beneficial despite some errors in the victim’s physical conditions during the escape.

Furthermore, efforts have been put into trying to minimise the risks of fire accidents and to improve the accuracy of responding to real fires or false alarms. Last year, the FSD worked with the EMSD to enhance the fire alarming system in the FSD Service Academy. The system could alert members through mobile notifications with precise locations wherever smoke is detected. The system was also put in use in the Tuen Mun-Chek Lap Kok Tunnel and hotels. In addition, the UK has also recommended the installation of Arc Fault Detection Device in certain locations including houses to prevent electrical fires when there are loose connections of wires.

But after all, we, the citizens, should be the ones holding the biggest responsibility to prevent fire accidents from happening. Un-attended cooking, combustion with flammable materials, electricity overloading……can all be halted if we pay attention to fire safety.

What a lecture from Prof. Lee! I genuinely enjoyed it very much.