What is one indicator of a malfunctioning gas appliance?

A yellow or orange flame instead of a blue flame is a clear indicator of a malfunctioning gas appliance. A blue flame is a sign of proper combustion, indicating that the appliance is operating efficiently and safely. In contrast, the presence of yellow or orange flames suggests incomplete combustion, which can be caused by several factors, such as a blockage in the combustion air supply or issues with the burner. This incomplete combustion can lead to the production of carbon monoxide, a dangerous and potentially lethal gas. Therefore, observing a yellow or orange flame should prompt immediate investigation and potentially servicing of the appliance to ensure safety and proper operation.