A fire that engulfed a home in Parry Avenue in the early hours of June 9 last year could have been caused by drone batteries left to charge overnight, a coroner's court heard yesterday.
Calling it a "tragic misadventure", State Coroner Marvin Bay said the fire was "accidental in nature" and "electrical in origin". He found no basis to suspect foul play.
In just two hours, businessman Tang Hui Jen's home off Yio Chu Kang Road, where his four-generation family lived, was reduced to a charred state.
The blaze claimed the lives of his 64-year-old wife Angeline Tan and his Australian business partner of 30 years, Mr Ian Johnson, 74, who was a guest in their home.
Six people, including two firefighters, sustained minor smoke inhalation and heat-related injuries.
The fire started at about 3am in the living room of the two-storey semi-detached house, where three drone lithium polymer batteries had been left to charge on the carpeted floor beside the sofa.
Avoid charging devices overnight, say experts
When it comes to charging electronic devices, be cautious and avoid leaving them plugged in overnight, say experts.
Drones, mobile phones, laptops and other mobile appliances typically use lithium batteries, which carry a slight risk of catching fire if they are not properly charged or are of poor quality, said Associate Professor Tseng King Jet of Nanyang Technological University's (NTU) School of Electrical and Electronic Engineering.
Lithium batteries are more susceptible to overheating than lead-acid or alkaline batteries, said Associate Professor Madhavi Srinivasan of NTU's School of Materials Science and Engineering.
While standard quality-certified devices use batteries with safety protection circuitry that can handle accidental overcharging, she said "it is in general a good practice not to leave gadgets with lithium ion batteries charging for a longer duration than required".
"People should try to buy quality batteries and not go for cheap batteries, especially when it comes to lithium ion batteries," said Prof Madhavi.
Prof Tseng advised consumers to avoid using chargers that implement fast charging, as these may carry a higher risk of the battery overheating and catching fire. Devices and their chargers should also be put in a well-ventilated area, he said.
Tiffany Fumiko Tay
The batteries were for a multirotor service drone, the G4 Surveying Robot, that Mr Tang and Mr Johnson intended to import and distribute locally.
Other electrical items, such as an electrical reclining sofa set and massage chair, were also not completely switched off. There were also power extension sockets near the sofa and running under the living room carpet that were used to charge various household electrical items.
Domestic helper Noemi Lozano Corpuz was asleep in a room on the first floor when she was awakened by the smell of smoke.
Upon seeing the sofa area on fire, she rushed to two bedrooms on the second floor to alert five other occupants before she escaped through the back door with Mr Tang's father, Mr Tang Song Bak.
Six of the 10 occupants were able to evacuate by climbing out of their bedrooms before the Singapore Civil Defence Force arrived.
Mr Tang Hui Jen, who initially believed it was a small fire, hid in the master bedroom toilet with his wife and used wet towels to facilitate their breathing. Hoping to put out the fire, he filled a pail in the toilet and opened his room door, only to be confronted by thick black smoke.
In a state of shock and panic, Mr Tang climbed out to the balcony and jumped off onto the porch, sustaining a head injury and an arm fracture. Only after jumping did he recall that his wife was still in the toilet.
Six pump ladders and five supporting vehicles were activated to put out the fire, which was eventually quelled at 6.45am.
Mr Johnson was found in the corridor next to a guest bedroom, while Madam Tan was inside the master bedroom toilet. They died of extensive burns. Both rooms were on the second floor.
Mr Johnson had reportedly reassured Mr Tang that it was safe to leave the batteries to be charged overnight as they had extra safety features. Mr Johnson was the co-director and designated technical expert of their company, and had attended a course in Germany on operating the drones.
However, the coroner cautioned against leaving drone batteries or similar devices to charge overnight entirely unattended.
"Charging of batteries of drones... should be done only with supervisory presence of persons who can intervene in the event of an exigency, such as an adverse reaction when the battery is overcharged or damaged," he said.