[Stoves] Personal Particulate Monitor

[Andrew Heggie]

I've made the subject a bit more appropriate, comments below:


On Wed, 12 Sep 2018 at 19:33, Norbert Senf <norbert.senf at gmail.com> wrote:
>
> Hi Andrew:
> I have not used one, or seen a sensor in the flesh.
> My friend in Fairbanks Alaska says they have local neighbourhood groups starting
> an ambient air sampling program, using a new device that attaches to a smartphone.
>
> It is an LED or LED laser light source, with a sensor placed off-axis, so that it only
> catches scattered light. Additional electronics convert it to a particle count, which may be why
> there is an upper limit. A while back we were looking at one that was calibrated to give
> particle counts at 2 different sizes. Apparently they are used quite widely in China for personal
> monitoring of indoor air quality in conjunction with air cleaning devices.

I think this latter is much like the device I have. It gives a count
for PM10 and PM2.5.
>
> I doubt whether the flow speed through it would affect the particle concentration, ie if you
> put a sampling tube on it.

This confuses me somewhat, surely to measure concentration one needs
to know how much air is passing the sensor and then count the light
reflected off particles. or is there another way of knowing a
concentration?  I thought perhaps it assumed the fan drew a fixed
volume per second and then the reflections were counted and calculated
as a mass in that volume. If a restriction from a tube reduces the
flow then a smaller volume passes but the sensor still counts the now
lesser number of reflections, giving a lower reading??
>
> However, if you put a sampling tube with a T inlet for dilution air
> you might be able to get a known dilution ratio, simply from knowing the  PM concentration in
> two different air sources, which are each individually measurable with the instrument within its
> given range.  ...........Norbert
>

Yes Frank Shields mentioned using a gas with a known purity, like
helium to do this but that's a bit beyond me.