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I'm unable to find good sources to make myself an AQI(Air quality Index) measuring device. All I was able to find was the way it is calculated in different regions. But I need some help with the technology used to measure the concentrations of different pollutants like SO2, NOx, PM10, PM2.5, etc.

Are there any good papers or patents on the technology used to measure the AQI?

Any help is appreciated. Thanks.

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The AQI calculation does not require that all pollutants be measured. Instead, it uses the pollutants that are available and then uses a function (chosen by the overarching regulatory agency) that equates health risk categories to the pollutant concentrations. The pollutant with the highest health risk (at present concentrations) will effectively determine the corresponding AQI. See here for how the USA EPA computes their AQI.

In order to detect the most commonly monitored pollutants, you would need an ozone analyzer and a PM2.5 monitor. This is quite expensive. A good single-pollutant monitor will cost thousands of dollars to purchase and many continuing costs. You will also need calibration equipment and standards. Depending on what AQI network you will be using as a reference, the model of instrument that you use will have to meet certain specifications in order for the data to be valid. Teledyne is an example of a company that makes equipment that would meet the qualifications for the USA AirNOW network. You may also find of interest their nice AQI calculator.

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    $\begingroup$ Thanks, but the I wanted to know about the technology like sensors and stuff. Not the info on calculating AQI or existing products. $\endgroup$ – iamgr007 Dec 27 '16 at 16:18
  • $\begingroup$ I think you are missing the point. Sensors don't measure the AQI. $\endgroup$ – farrenthorpe Dec 27 '16 at 16:51
  • $\begingroup$ I know how to calculate the AQI, I mentioned that in the question. I need the data from the air which can be measured by sensors which in turn are used to calculate the AQI. Am I clear? $\endgroup$ – iamgr007 Dec 27 '16 at 16:59
  • $\begingroup$ Yes I saw you edited your question. Did you look at the Teledyne link in the answer? $\endgroup$ – farrenthorpe Dec 27 '16 at 17:19
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    $\begingroup$ Perhaps you should research what type of sensor (that actually exists) you would like to make. Then you could form a question that is answerable to your liking. $\endgroup$ – farrenthorpe Dec 27 '16 at 17:32
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Ambient or roadside concentrations for each pollutant, over different averaging times, will be converted into an index value. In general, there are three common methods to achieve this. The most popular approach is often called the US-based system. Pollutant concentrations for each pollutant are transformed onto a normalised numerical scale of 0 to 500, with an index value of 100 corresponding to the primary National Ambient Air Quality Standard (NAAQS) for each pollutant (USEPA, 2006, website 14). Places like Singapore, China, Thailand, Malaysia, South Korea, Taiwan, Hong Kong, and Macau designed their AQI /API systems based on the US model. The key reference point of these systems would be the index value of 100, which is based on the short-term air quality standards of the respective jurisdictions. Very often, the index value of 50 is anchored to the long-term air quality standards.

A similar approach is being used in Australia, whereby pollutant concentrations are also being transformed onto a scale. There, however, a linear or proportional scale is used instead of a normalised scale (i.e. a scale which takes the variation into account), and the index is then calculated in direct proportion to the air quality standards or environmental goals (Ove Arup, 2007, 1). Moreover, the scale used in New South Wales is different from the one used in Queensland, Victoria, and Adelaide (in South Australia). In New South Wales, an index value of 50 means that the pollutant concentration is equal to the standard level. For the other states and cities, the index value of 100 carries the same meaning (Ove Arup, 2007, 1; website 4).

The third approach is the banding system, which is more popular in European countries like the UK and France (websites 3, 13). The main deviation is that instead of using an index scale of 0 to 500, a scale of 0 to 10 is being used. For the UK system, this index scale of 10 is further broken down into four bands of ‘low’ (1-3), ‘moderate’ (4-6), ‘high’ (7-9) and ‘very high’ (10) (website 13). The key reference point for this banding system is the breakpoint value between the ‘low’ and ‘moderate’ bands. The lower bound of index value 4 is set to correspond to the UK Air Quality Standards for all pollutants but NO 3 2. In this case, the 1-hour national standard for NO2 is 200 g/m , whereas the lower bound of index value 4 for NO2 is 287 g/m3 (website 13).

A Study of the Air Pollution Index Reporting System by Prof. Wong Tze Wai School of Public Health and Primary Care The Chinese University of Hong Kong

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