Haze is traditionally an atmospheric phenomenon where dust, smoke and other dry particles obscure the clarity of the sky. The World Meteorological Organization manual of codes includes a classification of horizontal obscuration into categories of fog, ice fog, steam fog, mist, haze, smoke, volcanic ash, dust, sand and snow.^[1] Sources for haze particles include farming (ploughing in dry weather), traffic, industry, and wildfires.

Seen from afar (e.g. approaching airplane) and depending upon the direction of view with respect to the sun, haze may appear brownish or bluish, while mist tends to be bluish-grey. Whereas haze often is thought of as a phenomenon of dry air, mist formation is a phenomenon of humid air. However, haze particles may act as condensation nuclei for the subsequent formation of mist droplets; such forms of haze are known as “wet haze.”

The term “haze”, in meteorological literature, generally is used to denote visibility-reducing aerosols of the wet type. Such aerosols commonly arise from complex chemical reactions that occur as sulfur dioxide gases emitted during combustion are converted into small droplets of sulphuric acid. The reactions are enhanced in the presence of sunlight, high relative humidity, and stagnant air flow. A small component of wet haze aerosols appear to be derived from compounds released by trees, such as terpenes. For all these reasons, wet haze tends to be primarily a warm-season phenomenon. Large areas of haze covering many thousands of kilometers may be produced under favorable conditions each summer.

The 2015 Southeast Asian haze is an air pollution crisis affecting several countries in Southeast Asia, including Brunei, Indonesia (especially its islands of Sumatraand Kalimantan), Malaysia, Singapore, Southern Thailand, and Vietnam, Cambodia and the Philippines.

The haze has affected Indonesia from at least late June,^[6] eventually turning into an international problem for other countries from September. It is the latest occurrence of the Southeast Asian haze, a long-term issue that occurs in varying intensity during every dry season in the region.^[7] It is caused by forest fires resulting from illegal slash-and-burn practices, principally on the Indonesian islands of Sumatra and Kalimantan, which can then spread quickly in the dry season.^{[8][9][10][11][12][13][14][15][16]}

On 4 September 2015, the Indonesian National Board for Disaster Management stated that six Indonesian provinces had declared a state of emergency due to the haze; they were Riau, Jambi, South Sumatra, West Kalimantan, Central Kalimantan and South Kalimantan.^[17] On 14 September, a state of emergency was again declared in Riau, this time by the Indonesian government.^[13][18] Thousands of residents of Pekanbaru, Riau’s capital, fled to the nearby cities of Medan andPadang.^[19][20] In late September, the Pollutant Standards Index (PSI) of Indonesia hit a record high of 2,300, recorded in the province of Central Kalimantan.^[21] More than 28 million people in Indonesia alone are affected by the crisis, and more than 140,000 reported respiratory illness.^[5][22]

The Indonesian government has estimated that the haze crisis will cost it between 300 to 475 trillion rupiah (up to S$47 billion) to mitigate.^[23] School closures due to the haze have been implemented in Indonesia, Malaysia and Singapore; this affected nearly four million students in Malaysia alone^[24][25][26] Among the events disrupted or even cancelled due to the haze were the 2015 FINA Swimming World Cup in Singapore and the Kuala Lumpur Marathon in Malaysia.

(Source: Wikipedia)

As a precaution, to avoid sickness caused by this situation, we must wear N95 mask when doing outside activities. UTM has taken precautions to postponed classes due to unhealthy API readings and provide N95 mask at the UTM clinic.