It’s fascinating to read the ISO 19867 Standards for cookstoves and I agree with a lot of it. Many of us in the ‘stove world’ were involved for years in creating those documents. One of the big improvements is testing stoves at high, medium, and low power while reporting the results with the firepower.

We forgot to do that in the International Working Agreement started in Peru at the Partnership for Clean Indoor Air meeting in 2011. Since stoves generally make fewer emissions at low power it was a temptation to reduce the firepower and achieve a higher score on the Tiers. Since firepower was not seen on the Tier scorecard, it was really not possible to compare performance. And as we know, people tend to like high power stoves. It’s so great that this problem has been fixed in ISO 19867.

How to get a Tier 5 score for emissions? Use a chimney.

Santa Claus in a chimney
Santa understands the importance of chimneys… Happy Holidays from the Aprovecho team!

The chimney transports most or all of the PM2.5 and CO out of the kitchen. Only “fugitive” emissions escape into the room. In ISO 19867 the fugitive emissions are used for the emission rate values. For unvented stoves, total emissions are used for the emission rate values. Just make sure that your chimney and stove do not leak.

It makes sense. Here in rural Oregon, unfortunately, smoke pours out of chimneys all day and night as folks stay warm with wood. Heating stoves can be very smoky! The airtight chimney and stove get essentially all of the smoke outside of the building where concentrations are and stove get essentially all of the smoke outside of the building where concentrations are diluted.

Now, of course, at ARC we try to combine high combustion efficiency with effective chimneys. We need to protect the quality of the outside air, as well. The combination is intended to protect indoor and outdoor air. If the outdoor air is polluted it is less effective in lowering harmful concentrations. Combustion efficiency is always great and to protect health it must increase when the outside air quality is degraded. In Beijing you don’t want to add one more milligram of smoke into the air!

An indoor/outdoor air quality planning tool.

Sam Bentson created an excel spreadsheet that explains how protecting indoor and outdoor air quality are related. You can download the spreadsheet here, and learn how to use it for project planning: