The air quality was at an unhealthy level in Seberang Jaya and a moderate level in three other locations today.
The Department of Environment (JAS) website said Seberang Jaya had an air pollutant index reading of 151 as of 10am.
The API reading was at the moderate level in Minden (95), Seberang Perai (91) and Balik Pulau (82).
An API reading of 0 to 50 indicates good air quality; 51 to 100, moderate; 101 to 200, unhealthy; 201 to 300, very unhealthy and 300 and above, hazardous.
Meanwhile in Kota Bharu, residents began wearing face masks following the drop in air quality due to haze.
Kota Bharu and Tanah Merah recorded API readings of 107 and 104 respectively yesterday.