Rare 'normal' PM2.5 in 3 regions on Oct 18; PSI at season-high 230 in western Singapore

No, this photo of Punggol isn't one taken on better days.

Clear skies and good air quality have been in short supply since Oct 5, when Singapore started recording 24-hour Pollutant Standards Index (PSI) readings in the unhealthy range.

Singapore calculates its PSI based on six pollutant particulate matter — PM10 and PM2.5, sulphur dioxide, nitrogen dioxide, ozone and carbon monoxide.

With one-hour PM2.5 concentration readings in the high and very high bands over the past two weeks, PSI readings have consequentially reached the very unhealthy range, including the season-high of 230 in western Singapore at 10am and 11am on Sunday (Oct 18).

The one-hour PM2.5 reading reflects current air quality conditions, making it a useful indicator when planning immediate outdoor activities.

Advisories on immediate outdoor activities are also given based on the varying concentration readings.

At 11am on Sunday, PM2.5 was in the normal band (0 to 55µg/m3) in northern, eastern and southern Singapore.

In this condition, all persons, including those who are vulnerable, may continue with normal activities.

Meanwhile, concentrations readings in western (142) and central (88) Singapore were in the elevated band.

This means that healthy persons should reduce strenuous outdoor activities for the next hour, while vulnerable persons should avoid strenuous outdoor activities for the next hour.

As of 12pm, PM2.5 readings ranged from 52 in the northern region to 136 in the west. The next lowest concentration readings of 58 and 61 were in eastern and southern Singapore respectively.

PSI remains in the very unhealthy range in western Singapore (227).

Elsewhere, PSI ranges from 127 in the northern region to 180 in central Singapore.

Why this is happening

In its daily haze situation update on Saturday night , the National Environment Agency (NEA) said that with winds forecast to blow from the south-southeast or south, there could be a reduction in smoke haze from Kalimantan to Singapore.

However, it did caution that some smoke haze from Sumatra may still drift towards Singapore.

Checks on the Meteorological Service Singapore's weather microsite show that winds are from the south at 11am.

During a whole-of-Government press conference on the haze situation on Friday afternoon, Sustainability and the Environment Minister Grace Fu had pointed out that the situation could improve by end-October or early-November as winds become lighter and more variable during the inter-monsoon period.

By early-December, with the onset of the northeast monsoon, any haze from Sumatra and Kalimantan will blow in the direction away from Singapore, she added.

But before you head over to the northern, eastern and western regions for fresh(er) air — check the latest PM2.5 readings before taking part in any outdoor activities.

不，这张榜鹅的照片并不是在天气晴朗的时候拍摄的。

自 10 月 5 日以来，新加坡的 24 小时污染物标准指数 (PSI) 读数开始处于不健康范围，晴朗的天空和良好的空气质量就一直很稀少。

新加坡根据六种污染物颗粒物（PM10 和 PM2.5、二氧化硫、二氧化氮、臭氧和一氧化碳）来计算其 PSI。

过去两周，PM2.5 浓度一小时读数一直处于高位和非常高位，因此，空气污染指数 (PSI) 读数已达到非常不健康的范围，其中新加坡西部地区在周日（10 月 18 日）上午 10 点和 11 点达到了本季最高值 230。

一小时 PM2.5 读数反映了当前的空气质量状况，因此是计划近期户外活动时的一个有用指标。

根据不同的浓度读数，还会发布有关立即进行户外活动的建议。

周日上午 11 点，新加坡北部、东部和南部的 PM2.5 浓度处于正常范围内（0 至 55µg/m3）。

在这种情况下，包括弱势群体在内的所有人，都可以继续进行正常的活动。

与此同时，新加坡西部（142）和中部（88）的浓度读数处于较高水平。

这意味着健康人群应在接下来的一个小时内减少剧烈的户外活动，而体弱人群应在接下来的一个小时内避免剧烈的户外活动。

截至中午12点，PM2.5浓度从北部地区的52到西部地区的136不等。浓度次低的地区分别是新加坡东部和南部，分别为58和61。

新加坡西部地区的 PSI 指数仍然处于非常不健康的范围内 (227)。

其他地方，PSI 值从北部地区的 127 到新加坡中部地区的 180 不等。

为什么会发生这种情况

新加坡国家环境局（NEA）在周六晚间发布的每日雾霾情况更新中表示，由于预计风向将来自东南偏南或正南方向，从加里曼丹到新加坡的烟雾可能会减少。

不过，该机构也提醒说，来自苏门答腊的一些烟雾可能仍会飘向新加坡。

查看新加坡气象局天气微网站可知，上午 11 点风向为南风。

周五下午，政府就雾霾情况举行了全员记者会。永续发展及环境部长傅海燕指出，随着季风间歇期风力减弱且变化无常，雾霾情况可能会在10月底或11月初有所改善。

她补充说，到 12 月初，随着东北季风的到来，来自苏门答腊和加里曼丹的任何雾霾都会向远离新加坡的方向吹去。

但是，在你前往北部、东部和西部地区呼吸新鲜空气之前——在参加任何户外活动之前，请查看最新的 PM2.5 读数。