When installing unvented space heaters, what must be avoided to ensure safety?

When installing unvented space heaters, ensuring that they operate safely is paramount. Using an unvented space heater as a primary heat source should be avoided because these heaters do not provide adequate ventilation and rely on the oxygen present in the room for combustion. This can lead to the buildup of harmful gases such as carbon monoxide, which can pose significant health risks. In addition, these heaters often do not adequately heat a space over extended periods, which increases the risk of exposure to dangerous conditions, including asphyxiation or even fire hazards if not monitored.

While other options address potential concerns with heat distribution or environmental factors that could affect safety, relying on unvented space heaters as the main source of heat presents the most critical risk. Always ensuring adequate ventilation and monitoring conditions in a space where such heaters are used is vital to maintaining safety.