Pet owners should carry their animals into the lift as a sure way to prevent accidents like the one in Tah Ching Road from recurring, lift experts told The Straits Times.
Another precaution, they suggested, would be to upgrade or retrofit older lifts here to include newer safety technology.
Lift and escalator engineer Kok Peng Koon, 80, said that last month's accident could have been avoided if the lift in question had a more modern multi-beam or "door curtain" sensor.
"These sensors, which sometimes have almost 200 beams for one lift, are close to 100 per cent foolproof," said Mr Kok, who has 38 years of industry experience.
"Even if you put a thin strip of paper between the doors, they will open," added the independent authorised examiner for lifts.
The 19-year-old lift which severed Madam Khoo Bee Hua's left hand last month has a single-beam infra-red sensor located about 250mm from the lift floor. The lift doors had closed on her dog leash as they were unable to detect it.
Lift engineer Quah Eng Hing, 65, said that upgrading lift door sensors is the "best solution" to avoid future accidents.
"Newer Housing Board lifts now are among the safest in the world. They have an infra-red curtain that is so dense, with criss-crossing beams that can even sense objects in front of the doors," said Mr Quah, also honorary secretary of the Singapore Lift and Escalator Contractors and Manufacturers Association.
Experts stressed that lifts like the one in Tah Ching Road are still safe to use.
But passengers should make it a point to ride lifts carefully, said engineer Dominic Cher, 47. This includes keeping clear of the doors and watching out for leashes.
"It's best to carry your dog when you go into the lift - the same way you would carry your child," said Mr Cher, who is also an independent authorised examiner.
"If you are not careful when using lifts, even if they have multi-beam sensors, things could still happen," he added. "It's hard to predict when things can break down."
As for how a gap could appear between the cabin door panels, as it did in Madam Khoo's case, experts said that this is due to the "inherent" design of the lift. Lift doors hang on rails at the top, so any force at the bottom can cause them to be prised open.
But Mr Kok and Mr Cher noted that the Singapore Standard code of practice for lifts does not specify the permissible limit of such gaps.
In response to queries yesterday, the Building and Construction Authority said the lift in Tah Ching Road remains suspended and has to be inspected again before it resumes operation. It added that the Commissioner of Buildings will lift the suspension notice only "after he is satisfied that a thorough inspection has been conducted".
Yeo Sam Jo