Gas-fired appliances like furnaces, boilers, and water heaters create gases as a byproduct of the combustion process. In order for these appliances to work safely, they must be vented properly and maintain a proper draft to make sure the gases exit your home. A safe burn is represented by having the correct mixture of oxygen, carbon monoxide, and carbon dioxide. An improper mixture can mean poor performance of your system and, even worse, a safety concern. According to the heating experts at Quality Plumbing & Heating Inc., these components can only be checked by using a combustion analyzer.