Singapore's Pollutant Standards Index (PSI) continued to inch up after falling in the late afternoon, with the three-hour PSI at 91.

The 11pm update saw the PSI continuing to rise slightly, after a peak reading of 326 at 10am and before the PSI fell to its lowest today at the 5pm update of 73.

Air quality improved today after Friday afternoon's all-time high of 401, surpassing the previous worst reading here in 1997 of 226,

The Ministry of Health (MOH) and the People's Association (PA) together announced on Saturday evening that the distribution of free N95 masks to poorer household will begin on Sunday morning.

Households with a per-capita income of $900 or less are each eligible to receive four free N95 masks, and may visit the Community Clubs/Centres (CCs) from 9am Sunday to collect them.

They will be verified by their Blue Community Health Assist Card, or through a self-declaration of income. Those with pre-existing diseases, chronic medical conditions, heart and respiratory conditions and have difficulty getting masks may also approach the CCs for help.

The joint statement added that Singapore Armed Forces soldiers will be transporting the masks to community centres and community clubs islandwide, after which the PA's 33,000 grassroots leaders will assist in distributing them.

Air becomes "hazardous" when the index passes 300, a reading between 101 and 200 is "unhealthy". People can resume normal outdoor activities if the reading dips below 100.