How do balloons cause MRT train faults?

“Hold them Tightly — Do you know that BALLOONS, especially the metallic shiny ones, can STOP a train?” is a warning that is appearing in some MRT stations along the North East Line (NEL).

Posters warning commuters about the dangers of releasing balloons inside MRT stations began appearing in MRT Stations on the NEL two months ago, and commuters reacted with disbelief online.

In a discussion thread on HardwareZone, netizens questioned whether balloons really had such destructive potential.

According to the Land Transport Authority, last year’s train disruption on 6 April was traced to a balloon which had slipped into the tunnel at Boon Keng station, reported the Straits Times. When the balloon came into contact with the electrical insulator of the overhead power supply system on the ceiling of the tunnel, it triggered an electrical fault.

“But how can the balloons enter the tunnel?” asked user Morgan23 on the forum thread. Another user questioned how frequently balloons caused such faults. “As if there are many balloons?” wrote user stillgottheblues.

Yahoo Singapore has reached out to SBS Transit to find out how it is possible for balloons to enter the MRT tunnel, and the number of train faults caused by balloons since the disruption on 6 April last year.

The warning posters only appear along the stations on the NEL because only it is the only line using the overhead power supply system.

Many in the same discussion thread said they had not seen the posters at all. Some netizens questioned why balloons were singled out for this warning, when other objects such as earrings have also been the cause of door faults which can slow down an MRT.