How can passengers help themselves in a train breakdown?

SINGAPORE - The response from SMRT ("Circle Line train incident: SMRT explains cause and steps taken"; Wednesday) to Miss Melissa Lim Ya Hui's letter ("Commuters distressed and kept in the dark"; last Saturday) has raised some safety concerns.

Assuming we have a fully packed peak-hour train:

How much smoke is needed before the smoke detector is activated and the ventilation system shut?

What happens after the ventilation system is shut?

How long will the air supply last in a crowded train with no air-conditioning or ventilation, and with the presence of smoke in the cabin?

While the incident was resolved within five minutes, what happens if we have a case where staff are unable to reach the site of the breakdown for hours, and the system is not restored?

What options are available to passengers trapped in the train?

Are there manual systems to allow passengers to free themselves, or at least open windows to allow air to flow in?

This article was first published on January 2, 2015.
Get a copy of The Straits Times or go to straitstimes.com for more stories.