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Turbonetics

Senior Member
Feb 19, 2009
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#4
is this test really accurate for real life usage?
the test is done in a small box where most Air purifier should be able to do the job.
but for our house with much bigger space of Air to be purified,how many units do we really need to achieve such figures?
 

Octarine

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Jan 3, 2008
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#5
The PM2.5 figures are given as 'micrograms per cubic meter', the AQI calculations are done based on this value. Here we see the total particle count. Without a clear linking and reference between both the particle count is meaningless.
Secondly, the AQI and the warning levels also consider exposure time. Something that is completely ignored here.
 

#6
Hi all, for those whom are interested. The exact formula used by National Environment Agency (NEA) in calculating the Pollutant Standards Index (PSI) can be located here.

Cheers.
 

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#7
Also. I would like to clear up some confusion and unfounded rumours going on.

PM10 in the context used by National Environment Agency (NEA) is defined as atmospheric particulate matter < 10 µm in diameter thus atmospheric particulate matter < 2.5 µm in diameter (PM2.5) will be included as a subset as well. As an index including readings of Sulphur Dioxide (SO2), Carbon Monoxide (CO), Ozone (O3), Nitrogen Dioxide (NO2) with differing segmented regression breakpoints and unit of quantity as per the formula above, thus it cannot be compared directly solely to the PM2.5 readings which is in µg/m³.

As a well respected member of the international meteorological community, the Meteorological Services Singapore (MSS) will absolutely never ever manipulated data and information in deliberate attempts at disseminating PSI readings through false data injection.
 

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Octarine

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#8
Hi all, for those whom are interested. The exact formula used by National Environment Agency (NEA) in calculating the Pollutant Standards Index (PSI) can be located here.
This formula is also described somewhere on the website of NEA. But to me, this is only half the answer.
Main question is (not to you): Why is the PM2.5 reading not included into the PMI, although this is already a standard in many countries, not just since yesterday. It is well known and established that the particles with a size smaller than 3 micrometers do have a negative effect on the health of people.
It seems, only after a mounting pressure and questions from the public the PM2.5 readings were published, but without any scale or interpretation as to which levels of particle concentration refer to which air quality levels. Neither NEA nor anybody else has clarified the reasons for this (imho questionable) approach.
Using the absolute readings and linking them to the scale used in other countries it reveals the unhealthy levels of PM2.5 concentration the public was exposed to in the past weeks when the official PMI was only published as 'Moderate'. Why?
 

#9
This formula is also described somewhere on the website of NEA. But to me, this is only half the answer.
Main question is (not to you): Why is the PM2.5 reading not included into the PMI, although this is already a standard in many countries, not just since yesterday. It is well known and established that the particles with a size smaller than 3 micrometers do have a negative effect on the health of people.
It seems, only after a mounting pressure and questions from the public the PM2.5 readings were published, but without any scale or interpretation as to which levels of particle concentration refer to which air quality levels. Neither NEA nor anybody else has clarified the reasons for this (imho questionable) approach.
Using the absolute readings and linking them to the scale used in other countries it reveals the unhealthy levels of PM2.5 concentration the public was exposed to in the past weeks when the official PMI was only published as 'Moderate'. Why?
Octarine, you may want to give this short article entitled "Why is PM2.5 often higher than PM10? Is PM10 still a relevant measure?" a read.

It does answer some but not all of your questions. I'm sure when new standardised index are approved by the World Health Organization (WHO) and World Meteorological Organization (WMO) taking into account PM2.5 readings, we will rapidly adopt in no time. Right now, even for "Air Quality Index (AQI)", the formula differs separately from each individual nation to each individual nation.

Cheers.
 

Octarine

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#10
It does answer some but not all of your questions. I'm sure when new standardised index are approved by the World Health Organization (WHO) and World Meteorological Organization (WMO) taking into account PM2.5 readings, we will rapidly adopt in no time. Right now, even for "Air Quality Index (AQI)", the formula differs separately from each individual nation to each individual nation.
I have read this article since I also use this website to get additional information about the air quality situation.
Surely it will take along time to come to an agreement on global level about how the PM2.5 figures will be incorporated into AQI or its equivalents. In the meantime it would be helpful to have at least a general indicator or scale so that the public can see whether the level of PM2.5 is 'moderate' or 'hazardous'. Publishing the absolute figures without any scale or indication of health impact does not help much or only fuels rumours and speculations.
 

#11
I have read this article since I also use this website to get additional information about the air quality situation. Surely it will take along time to come to an agreement on global level about how the PM2.5 figures will be incorporated into AQI or its equivalents. In the meantime it would be helpful to have at least a general indicator or scale so that the public can see whether the level of PM2.5 is 'moderate' or 'hazardous'. Publishing the absolute figures without any scale or indication of health impact does not help much or only fuels rumours and speculations.
From my very own personal understanding, they are already working towards incorporating PM2.5 level readings separately as one of the main sub-index into the formula used for automatically computating the Pollutant Standards Index (PSI) after the recent unprecedented haze situation caught their pants down. There is already an interim measure in place to release relevant health advisories only after three hourly PM2.5 level readings exceeded a certain &#956;g/m3 critical threshold, I am not exactly certain of the rational behind this and will not go into further speculating details due to a lack of information not privileged for me as such.

As you said, it takes time. Time for our well remunerated Division I public service officers to conduct their own research specifically on our environmental and population sample in order to positively correlate findings from internationally established academic journals and scientific papers on adverse health effects of short term to long term exposure from concentrated PM2.5 levels. Get it peer reviewed / vetted before being approve by the higher up authorities. Something that doesn't happen overnight.

Meanwhile as mentioned previously, since PM10 in the context used by National Environment Agency (NEA) is defined as atmospheric particulate matter < 10 µm in diameter thus atmospheric particulate matter < 2.5 µm in diameter (PM2.5) will be included as a subset as well. One could still reliably refer to the PM10 level figures and take any actions / precautions as necessary to safeguard their love ones and themselves since a rise in the concentration of atmospheric particulate matter < 2.5 µm in diameter (PM2.5) will also definitely lead to a corresponding increase in the PM10 level readings as well.

Perhaps right now the best we can do is to use the same segmented linear regression breakpoints in the formula for both PM2.5 and PM10. e.g. A three hourly PM2.5 level reading with a concentration of 350 &#956;g/m3 will thus be reflected as a PSI of 200 indicating "unhealthy". I have noticed people utilising "AQI calculator" which will then place it in the range of "hazardous" but those are based on 24 hourly figures.
 

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