When living in the shadow of terrorism, "false alerts" must be seen as an oxymoron, because no alert is erroneous, given the grave risks involved. One hopes nothing sinister is ever uncovered. But if complacency sets in, then an alarm that is not taken seriously is the one properly called false.

All alerts deserve attention and steps taken should not be dismissed as being overcautious, especially after checks reveal the ordinariness of the things that had triggered precautions. In recent incidents at Woodleigh and Hougang MRT stations, flour was left at spots to mark a running trail in one case and a bag with household items was left unattended in the other. These led to the closure of the stations and the activation of emergency services. Did supervisors overreact?

If a real threat had been defused, station staff would have been lauded for their alertness. In the same way, one should commend the "better safe than sorry" approach taken in both cases and the calm response of commuters. These occasions help to engrave the need for eternal vigilance in the public psyche.

Flour looks similar to anthrax powder which can cause death in serious cases. And bags can conceal dangers, like the briefcase used to hide a bomb which killed train passengers in St Petersburg earlier this month. Train stations have been targets of terrorists for almost eight decades. In recent times, coordinated attacks have taken place, like those at a metro station and airport in Brussels last year. Such threats oblige all to remain alert and to not shy away from reporting anything suspicious. Any precautions taken should not be regarded as overkill. It's the failure to respond to threats that could prove to be the real killer.

Singapore is fortunate to have been spared the sort of attacks that have hit many cities in the region and beyond. Its best hope of continuing to do so rests on a population that stays ever vigilant.