So I have been cleaning up my garage, organizing the mess that is in there, and came across a bunch of smaller 2x4's (not treated lumber) that have been stained with an interior based stain. The biggest piece is probably 5 inches long. Most are cut at angles, and pretty worthless as far as future use in any project I may build. My question is, would using these pieces hurt my fireplace insert at all, if I use them in small quantities, mainly as kindling?