As Singapore's air quality deteriorated yesterday afternoon, many Orchard Road shoppers donned their masks on their day out on a public holiday.

The overall Pollutant Standards Index (PSI) reading hit 179-219 at 1pm, crossing into the unhealthy to very unhealthy ranges.

Many left their masks on as they walked in and out of malls along the shopping strip.

By 8pm, the 24-hour reading stood at 215-263, in the very unhealthy range.

If the overall 24-hour PSI goes above 300, air quality will be deemed hazardous.

In 2013, the three-hour PSI level hit a record 401 during the haze. Yesterday's three-hour reading at 8pm was 317.

Kok Xing Hui