I agree with wvcandleguy. The amount of wax is so small, it would never build up in the chimney. I use the firestarter bricks all the time, but I cut each one into six pieces. You could use any kind of wood for the sawdust, it has been kiln dried. I am going to make firestarers with my scrap wax, and I do woodworking, so I have an endless supply of sawdust lol. And as always, get your chimney cleaned every year. A chimney fire is not a good thing. Just ask, I had one four years ago in my woodburner chimney. Luckily, I was in the basement at the time, and got all the air shut off to it and snuffed it out. (was caused wrong size flue liners). But cost $2500 to repair. Now all my chimneys get cleaned every year.