document updated 14 years ago, on Sep 26, 2010
- space heaters are classified as either vented or unvented
- unvented heaters are inherently limited — no matter how efficient they are:
- they will ALWAYS put out carbon dioxide and lots of water vapor, and consume oxygen, which can eventually make the air literally unbreathable
- they always put out carbon monoxide and numerous other waste products
- unvented heaters should not be used for more than two hours a day