First post - found the forum while searching for an inexpensive source for Trioxane tabs.
Have used Trioxane (and the little brother Hexamine tabs) in the field a number of times.
You don't want to use these in an unventilated area - Carbon Monoxide for one. Other by products from the burning aren't good for you to breath either.
I find they're great for heating up water/food. Use them in the real or improvised stoves I've seen mentioned in prior posts. Generally, I've used a canteen cup on a couple of rocks or put the tab in small hole in the ground.