Sorry all I seem to have missed the continuance of this thread. In reply to APH I am talking from experience gained through over 40 years in the wood turning industry. It is rare but it can happen and it is an industry standard to keep shavings and sawdust seperate. Not every incident is recorded but when you consider how hot it can get in compost heaps and suchlike a pile of shavings mixed with dust can ignite. Even if you can not find evidence to support this the fact that someone (me)has gone to the trouble of advising against this mixture should be enough of a warning. I am not getting hysterical about H&S and saying this is what you should do because that is not my style, all I am saying is in my years in the wood trade it has been know to happen.