PETALING JAYA - Port Klang residents are hanging on to their face masks, as thick haze drove the API reading to a high of 495 Tuesday morning.
The Department of Environment recorded the latest reading at 8am. Only an hour earlier, the reading was at 487, a spike from Monday's evening's already hazardous reading of 319.
API readings between 51 and 100 are considered "Moderate", 101 to 200 as "Unhealthy" and 201 to 300 "Very unhealthy".
Any reading above 300 is "Hazardous" while readings above 500 come under "Emergency".
Selangor's port town is facing the worst haze in the state as the smoke travels north from Muar and Ledang in Johor, where a haze emergency had been declared on Sunday.
Port Klang has had very unhealthy API readings of over 280 since that day.
Other areas in Selangor closing in on the hazardous mark were Banting at 293 and Shah Alam at 297.
Kuala Selangor has a reading of 245, while Petaling Jaya has a reading of 216.
Across Malaysia, 19 areas are still labelled unhealthy and five locations very unhealthy.