[Stoves] PM discussion

[Norbert Senf]

A little complicated trying to quote the previous discussion points, but
here's what I've learned so far in my little slice
of PM measurement relating to wood:

- the EPA standard was updated from PM10 to PM2.5
- for domestic woodburning for heating, there is no difference, since 90%
of the woodburning PM is <1 micron.
- toxicity is not addressed

- I suspect that Crispin is correct that flyash is not that toxic, since it
is mostly minerals.
- however, coal has a lot more ash content than wood. Cordwood is 0.5 -
1.5% ash. Bark is more.  Coal can be up to 30%(?)  or so.
- since the ash constituents from coal date back to prehistoric times,
maybe there are concentrations of heavy metal, radioactivity, etc ??

- for domestic wood, there is a big split between OC and EC (organic carbon
and elemental carbon, aka tar and soot)
- tar comes from smoldering, and soot comes from quenching a flame
- tar is 10x as toxic as soot.

An older generation of common rural appliance known in the US as an
"outdoor boiler", which has literally a water cooled firebox, produces
100g/kg of PM, almost all of it tar.
A pellet stove or a masonry heater produces 1 g/kg of PM, almost all of it
soot.
Therefore, burning the same piece of wood, an outdoor boiler is conceivably
1000X as toxic as a masonry heater.

Norbert
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