PETALING JAYA: The haze has visibly returned to the Klang Valley despite the fact that Air Pollutant Index (API) on the Department of Environment’s (DOE) website reported ‘good’ to ‘moderate’ readings.

Residents noticed a sharp drop in the air quality Monday and could smell it in the air, with several parts in Kuala Lumpur and Selangor recording poor visibility.

However, some may be left puzzled as API readings for Petaling Jaya was 46, Shah Alam (51), Port Klang (55), Putrajaya (61), Cheras (45).

According to the DOE, the API readings are based on an average of readings over the previous 24 hours.

For example, the API readings reported on 10am on Monday would be the average reading taken between that time and 10am on the previous day.

Last Friday, acrid smog blanketed Singapore as the city-state was hit by the year’s first major outbreak of haze, an annual crisis sparked by forest fires in neighbouring Indonesia.

API readings are determined based on an international acceptable protocol which calculates the 24 hour averaging times for five criteria pollutants namely Particulate Matter of less than 10 micron (PM10), Sulphur Dioxide, Nitrogen Dioxide, Ground Level Ozone and Carbon Monoxide.

API readings of between 0-50 are considered good, moderate (51-100), unhealthy (101-200), very unhealthy (201-300) and dangerous (exceeding 301).

Any reading above 300 is “hazardous”, meaning the air quality is a hazard to high risk individuals and the public health in general.-thestar