I have read that pine and cedar are both bad, but cedar is supposed to be a little worse. I also learned years ago that corn cob can be horrible too. When it gets wet, it builds up a mold that is toxic to small mammals. After we learned this, the pet store I worked for kept it in very limited supplies and would only sell it to reptile (snake mostly) owners. This is about the only safe application. My glider is bad with the fleece also, but after researching there is one thing that I've not been able to find any negative information on against glider safety; Aspen crumbles. I love it. If there is any problem that anyone here has found, please correct me so I can stop and no one else takes this advice.