All schools in Johor, Terengganu and Kelantan will be opening as usual tomorrow after a week-long holiday since the air pollutant index (API) readings nationwide are still under 200 as at 4pm today.

The Education Ministry in a statement said the state education departments and district education offices should monitor the API readings issued from time to time by the authorities.

"If there are changes in the API readings to unhealthy (101-200) or very unhealthy (201-300), then they can take action at their respective levels under the circular on the measures to ensure the safety of students in areas affected by critical levels of haze," the statement said.

As at 6pm, the Department of Environment portal reported good air quality in eight areas, 27 areas (moderate) and 16 areas (unhealthy).

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 JOHOR BAHARU, state education department chairman Aminudin Adam said, as at 5.30 pm, the API in Pasir Gudang was 83, Kota Tinggi (64), Muar (95) and Johor Baharu (83).

He said if the API readings worsen tonight, the department would be informing the teachers to monitor the students to return to their homes if they attend schools tomorrow.

"If the API reaches 200 and above, the school management can close the school," he said.

Aminudin said only schools in the affected zones would be closed.

He said if the area recorded an API of 155, schools would be operated as usual but all activities outside the classroom would not be carried out.