Posted by: Matthew | June 2, 2010

Woodheaters standards are way too lax. Here’s the figures.

Have you ever wondered what the standards are for woodburners? I say they’re lax. The firewood industry claims they’re “healthy” and that woodsmoke was only a “historic” problem. For new woodheaters in Australia and NZ it is a woodburner that gives 1.5g of solids per 1kg of dry fuel. Of course this is so lax that in some towns like Arrowtown in Otago where monitoring has shown that using one of them leads to massive pollution the new regulations are going to be 0.7g per kg of dry fuel.

But we’ll stick to 1.5 grams per 1 kg since that is what new woodburners in Raumati South are allowed to have.

Of course in reality no one can actually meet those standards when using them anyway, because the standards don’t apply to the first half hour of the burning, and that is far smokier and it is if the person using it actually knew or cared about how to burn below the 1.5 grams per kg level. Which of course they don’t, because if they did know or care they wouldn’t be using one in the first place.

And of course there are no regulations for controlling older non-compliant woodburners in Kapiti anyway.

Now here are some back of the envelope calculations for Raumati South on a windless night when an inversion layer occurs.

I’m assuming that each block is 600 metres square, and there is an additional 400 metres for roads and parks. This means there are 1000 dwellings in a square kilometre. I am assuming that 50% of all households are burning a woodfire. I am also assuming that they are burning at 1.5 grams of smoke per 1kg of dry wood. I’ll assume they use 6 logs for the night, and it is approximately 10kg of wood. Therefore each burning house is putting out 15 grams of smoke. There are 500 burning houses in a square kilometre. So that is 7.5kg of smoke per square kilometre each evening.

The inversion layers aren’t high up in Raumati. They form between the dunes. I am going to assume that the top of the inversion layer is 10 metres above the ground. I am also assuming none of the smoke is escaping through the inversion layer. And that makes 750 milligrams of smoke per cubic metre by the end of the night.

In Otago they mark an excessive smoke event at 50 milligrams per cubic metre. It can be seen that it is very, very easy on a windless night to exceed that by factor of 25. So let’s see how this figure compares to some real figures. There aren’t any in the Wellington Regional Council area as they don’t do much in the way of measuring it. This week in Otago there was this report. Mosgiel reported a high of 103 mg per cubic metre.¬† Milton got a high of 140mg in 2009. Arrowtown got to 168mg in 2007. So my back of the envelope calculation may be high, but then again under those inversion layers in Raumati South I would believe it to be closer to 750mg per cubic metre rather than 100mg per cubic metre.

So what you say?

Well everytime you breathe you breathe between 390 and 500 mls of air, and you normally breathe between 12 and 20 times per minute. So that means you breathe between 400 and 600 litres of air per hour. Or in otherwords approximately 0.5 cubic metres of air per hour. And if that air is at just 50 milligrams per cubic metre, you will be breathing in 25 mg of wood smoke in an hour or 25o milligrams of smoke over a 10 hour night.

At 750mg per cubic metre of woodsmoke an hour (which I believe with the lax standards of woodburners in NZ, and a still night is certainly possible, maybe it’s a bit too high) you will be breathing in over 4 grams of woodsmoke during one night. This is 4 grams of some of the most deadly carcinogenic chemicals. 4 grams per night. And just because you’re all tucked up in your house thinking you’re safe, some of those chemicals are in the form of particulates and seep into your house through normal ventilation. These particulates are below 10 microns in diameter, and some are below 2.5 microns. The cells in your lung tissues have no defences against particles that small and they enter your cells and your bloodstream. 4 grams per night for 200 nights of winter for however many years and you will die early. The epidemiological studies seem to bear this out.

There is no escaping it. Woodsmoke is killing us in New Zealand and it is doing it right now, not historically.

It is not hyperbole to say that the NZHHA and the firewood companies and the people using woodburners are conspiring to murder New Zealand citizens.


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