Impacts of Unvented Space Heaters

Combustion of fossil fuels produces a variety of contaminants, many of which can be hazardous to health. Most combustion equipment in buildings vents these contaminants directly to outdoors, but products exist that release the contaminants directly to the indoor air. This article reviews the relevant combustion process, the contaminants and their acceptable levels in the context of ASHRAE standards and position documents, with particular emphasis on unvented residential space heaters.