Lift door sensors not 'absolutely foolproof' in preventing accidents: BCA

SINGAPORE - All lifts must be fitted with protective devices, but there is no guarantee that they will be absolutely foolproof to prevent lift accidents, the Building and Construction Authority (BCA) said.

The authority was responding to an investigation report by an authorised examiner over a lift accident in Jurong on Oct 9, in which an 85-year-old woman's left hand was severed.

In a statement on Monday (Nov 9), BCA explained that if lift doors were obstructed while in the process of closing, protective devices would automatically cause the doors to re-open.

According to BCA, some lifts are fitted with mechanical safety devices which triggered lift doors to re-open if they are pushed back by a certain amount of pressure.

Another safety device are the single-beam sensors, which triggers lift doors to re-open if a beam of infrared light emitted from one side of the door is obstructed.

"The lift that was involved in the incdent at Tah Ching Road was fitted with both a mechanical safety edge as well as a single beam sensor at the bottom of the doors," BCA elaborated.

BCA acknowledged that the likelihood of accidents could have been reduced had the lift been fitted with multi-beam sensors. These include 2D sensors, in which there are an array of beam sensors along the doors, or 3D sensors where the coverage of detection is extended to the areas around the doors.

But it noted that these sensors still have "blind spots", as the beams "cannot detect objects that are smaller than the spacing between beams".

The investigation report had found that there was nothing wrong with the lift in question, and that a dog leash that was looped around Madam Khoo Bee Hua's left wrist was too narrow for the sensors to detect.

The authority further explained that all types of sensors would be deactivated once the doors are almost closed to enable the doors to close completely.

"Hence, even with multi-beam sensors, there is no guarantee that it would be absolutely foolproof in preventing an incident like that which happened at Tah Ching Road."

BCA revealed that current provisions for lift door protective devices are on a par with international standards, and that it regularly conducts holistic reviews of lift safety standards, the latest of which began last year and will be completed by the middle of next year.

"BCA will work with the industry and lift owners to seek ways to enhance public awareness on the precautions to observe when using lifts," it said.

seanyap@sph.com.sg