Although the Air Pollutant Index (API) readings were at a moderate level yesterday, the light smell of smoke could be detected.

The API reading at 5pm for Seberang Jaya and Prai was 94, which was getting nearer to the unhealthy level.

On the island, the Department of Environment (DOE) monitoring station in Universiti Sains Malaysia (USM) recorded 82.

[ Blurred outlook: Buildings in Bandar Baru Air Itam are almost invisible at noon in Penang. ]

According to the state Meteorological Department, visibility in Bayan Lepas was at 4km at 2pm.

An API reading of between 0 and 50 is considered good, 51 to 100 (moderate), 101 to 200 (unhealthy), 201 to 300 (very unhealthy), and 301 and above (hazardous).

A medical practitioner said five asthma sufferers sought treatment at his clinic in Bayan Baru yesterday, adding that they faced breathing difficulties because of the haze.

State Welfare, Caring Society and Environment Committee chairman Phee Boon Poh had said that the forest fires in north Sumatra were the main cause of the haze.