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About unit of monthly report

Last update date March 11, 2019

When we express data of nitrogen dioxide (NO2) and sulphur dioxide (SO2), ppm is used as unit generally, but uses unit called ppb to make it easy to read number list in monthly report. In addition, even suspended particulate matter (SPM) uses another unit equally.
In this page, we explain relations with unit used in unit and monthly report used generally.

Up to 744 (31st X 24 hours) data are listed in monthly report on page 1, but there is difficult point that big things and small things of data are incomprehensible when a lot of data which zero follows like 0.001 ppm line up because it is number of same five characters only by having had a look.
Therefore, it is necessary to be easy to grasp numerical big things and small things in data forming a line a lot when it has making (print) of monthly report.
General losing decimal by (NO2) doing number 1,000 times in the case of 100 times, three digits in the case of 10 times, two digits in (NMHC) in (CO) in the case of item to display to decimal one digit, and treating for integer.
It becomes easy to keep numerical big things and small things under control by seeing the number of the figures of data (the number of the letters) when we become integer in this way.
With this, unit uses unit for monthly report, too.

For example, generally ppm (one per 1 million) is used, and unit of nitrogen dioxide (NO2) is displayed like 0.123 ppm in five characters (decimal three digits) including decimal point.
On the other hand, we use ppb (one per 1 billion) which is unit that did number of ppm 1,000 times not unit of ppm including decimal point to shorten character string to display number to print monthly report on 1 page when it is easy to look at the face and does in the case of monthly report, and to put in yokamifuku (for example, horizontal B4).
For example, when, in the case of NO2, credit converts 0.001 ppm into 1ppb, 0.001 ppm → 1ppb, 0.012 ppm → 12ppb, 0.123 ppm → As 123ppb and numerical size are reflected to the number of the figures, it becomes easy to keep numerical big things and small things under control.
In addition, we can lay out monthly report because the number of the indication letters of data decreases below three characters from five characters to occupy width of paper.

Relations with general unit and unit of monthly report
Measurement itemWith general unit
Decimal place
Unit of monthly reportRelational expression (unit conversion) of bothIndication example of both
Sulphur dioxide (SO2)ppmThree digitsppb1 ppm = 1000ppb
= 1,000*0.001 ppm
0.123 ppm → 123ppb
Nitric oxide (NO)
Nitrogen dioxide (NO2)
Nitrogen oxide (NOx)
Photochemical oxidant (OX)
Carbon monoxide (CO)ppmOne digit*0.1 ppm1 ppm = 10*0.1 ppm1.2 ppm → 12*0.1 ppm
Non-methane hydrocarbon (NMHC)ppmCTwo digitsX 0.01ppmC1ppmC = 100 X 0.01ppmc2.34ppmC → 234 X 0.01ppmC
Methane (CH4)
All hydrocarbons (THC)
Suspended particulate matter (SPM)mg/m3Three digitsμg/m31 mg/m3 = 1,000 μg/m3
= 1,000*0.001 mg/m3
0.123 mg/m3 → 123 μg/m3
Microparticulate matter (PM2.5)µg/m3Noneμg/m3  
The wind velocitym/sOne digit*0.1m/s1m/s = 10*0.1m/s1.2m/s → 12*0.1m/s
The direction of the wind16 directions16 directions  
TemperatureOne digit*0.1 degree Celsius1 degree Celsius = 10*0.1 degree Celsius23.4 degrees Celsius → 234*0.1 degree Celsius
Quantity of sunlightMJ/m2hrTwo digitsX 0.01MJ/m2hr1MJ/m2hr = 100 X 0.01mj/m2hr1.23MJ/m2hr → 123 X 0.01MJ/m2hr
Quantity of emission income and expenditure

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Environmental Planning Bureau environment Maintenance Division Environment Administration Division

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