Does anyone have any experience with wood-burning pool heaters? I am intrigued by the idea (and I have a lot of "free" wood, thanks to some awful weather last summer) but it also looks like it could go horribly wrong!

I want to know if they actually work, and whether their particulate emissions are controlled (like regulated fireplace inserts and stoves) or whether they are basically a fire in a box with some water pipes. I would use it to extend the season, so it wouldn't be in use for more than three months of the year.

Thanks

Alison