# How to measure air quality (especially PM2.5) from distance (scanning like a LiDAR)? [closed]

I have a bit of experience in measuring PM2.5 (fine particles in the (ambient) air 2.5 micrometres or less in size) using PMS5003 sensor. This sensor uses laser, photodiode and the fact that the air flow through the sensor has constant speed due to applied fan.

However, this sensor can measure PM2.5 only in one location. I want a device which would be capable of measuring air quality (particulate matter or anything else) from distance. So, in order to make a map of pollutants in the city I wouldn't need to provide sensor for every x meters. I'd like to just locate the LiDAR-like sensor on some high tower and scan some area.

What should I use to build such a device?

## closed as too broad by Voltage Spike, brhans, Armandas, Daniel Grillo, PeterJSep 16 '16 at 13:36

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• How far are we talking? – user86234 Sep 15 '16 at 15:11
• I don't think this is doable without unreasonably powerful lasers for the LIDAR. – pjc50 Sep 15 '16 at 15:12
• Any distance longer than 250 m would be better than what I have now. – Defozo Sep 15 '16 at 15:13
• @Defozo The only way I could imagine measuring Very long ranges would be with very powerful lasers. We're talking some of the very expensive, illegal ones. – user86234 Sep 15 '16 at 15:16
• What distance can I achieve with the legal ones? – Defozo Sep 15 '16 at 15:19

Both of these systems use ND-YAG lasers that are frequency tripled into the UV. NG-Yag lasers can be expensive (>$1000 to well over$100k), depending on power, rep rate and pulse size. They also need sophisticated free-space optical setups for both the laser itself (including the frequency triple stage) and the backscatter return path. On top of this they need sophisticated data analysis tools in order to get usable numbers out. These are primarily research tools.