Singaporeans are understandably distraught as their country is enveloped in stifling smog coming from the forest fires in the neighbouring country Indonesia since earlier this week. The forest fires on the Sumatra Island are apparently started by plantation owners and farmers hoping to clear the land.

Indonesia is planning to use cloud-seeding to unleash rain over Sumatra and put out the fires, but in the meantime, two other nations are robbed of clean and breathable air.

Need to catch up with the news? Here's 6 things that you must know about the smog covering a portion of Southeast Asia:

1. It has set a new PSI level record at 12 noon Friday.

The National Environment Agency has recorded the PSI of the country at a record-breaking 401 level, which stumped Thursday afternoon's 371. Fortunately, though, it slid to 168 at 3 p.m. But again, it doesn't necessarily mean that the reading would continue to decline.

For clarity, PSI stands for Pollution Standards Index, which was developed by the United States Environment Protection Agency to provide accurate and timely information about the daily levels of air pollution. It has five levels, from Good to Hazardous.

0 to 50 PSI means Good, 51 to 100 is Moderate, 101 to 200 is already Unhealthy, 201 to 300 is Very Unhealthy, and 300 and above is deemed Hazardous.

No health advisory is necessary if the PSI value is at Good and Moderate. For Unhealthy, persons with existing heart or respiratory ailments are advised to reduce physical exertion and outdoor activities. The general public should also reduce vigorous outdoor activities.

If the level is at Very Unhealthy, the elderly and persons with existing heart or lung disease are advised to stay indoors and reduce physical exertion and outdoor activity. Also, the general public should avoid any vigorous activity outdoors.

At Hazardous level with 301 to 400 reading, children, the elderly and persons with existing disease as well as the general population should avoid outdoor activity. For over 400 PSI level, the public should avoid outdoor activities, and keep their windows and doors closed.

2. The smog is expected to last for weeks.

Unfortunately, even though the PSI level has decreased for the past three hours, Singapore Prime Minister Lee Hsien Loong has warned that it looks like the smog would remain in the country until the end of September.

As for now, hospitals are preparing for an increase in patients with asthma, bronchitis, and conjunctivitis cases. More than 100 companies in the nation have sent their staff home even before the government issued any advisory. Also, school closure is being seriously considered.

3. A part of Malaysia is also badly affected by the haze.

The air quality of the Malaysian capital, Kuala Lumpur, remains largely unaffected, but southern state Johor has been hit hard by the choking haze. The PSI level of the town Muar rose to 383 around noon on Thursday, which prompted officials to suspend schools.

Other towns in Johor were recorded to have Unhealthy level of PSI as well.

4. This isn't the first time Singapore has been enveloped in smog from Indonesia's forest fires.

Both Singapore and Malaysia are no strangers to smog coming from the raging forest fires in the Sumatra, Indonesia, often being hit in the middle of the year. But the air pollution levels that have besieged the countries this year are by far the worst. And that's why the diplomatic ties of the countries are in danger.

5. Singapore demands action from Indonesia; Indonesia responds by saying Singapore is "acting like children."

The severity of the pollution has prompted Dr. Vivian Balakrishnan, Singapore's Environment and Water Resources Minister, to write on his Facebook page, demanding "definitive action" from the other country.

"This is now the worst haze that Singapore has ever faced," he wrote. "No country or corporation has the right to pollute the air at the expense of Singaporean's health and wellbeing."

But Indonesia thought that Mr Balakrishnan should have conveyed his statements in a more diplomatic channel.

"Singapore should not act like children, making all that noise," Agung Laksono, coordinating minister for People's Welfare, said.

He added that, "This is not what the Indonesian nation wants, it is because of nature."

Indonesian officials have also suggested that Singaporean companies and other foreign palm oil investors are also to be blamed for the fires, which Singaporean palm oil companies have denied.

6. Indonesia remains the only member of the Association of Southeast Asian Nations that hasn't approved a 2002 agreement on reducing haze pollution yet.

This has frustrated Singapore as well.

"The persistent inability of Indonesia to address the haze problem despite and Asean agreement some years ago concluded to resolve the issue raises serious concerns about Indonesia's ability to play a future leadership role in Asean if it cannot adhere to its Asean commitments and obligations to its Asean neighbours," Asia chief economist Rajiv Biswas was quoted by The Wallstreet Journal as saying.