What are the potential consequences of a blocked chimney?

A blocked chimney can have severe consequences for both safety and the efficiency of a combustion appliance. When a chimney is obstructed, it prevents the proper venting of combustion gases, which can lead to smoke backing up into the living space. This smoke not only creates a health hazard due to the inhalation of harmful gases, such as carbon monoxide, but it also significantly increases the risk of a fire. When smoke accumulates and cannot escape, it can ignite in the chimney or within the structure, leading to potentially devastating fires.

In contrast, other options like increased fuel efficiency, improved draft, or no significant impact do not accurately reflect the critical dangers posed by a blocked chimney. A healthy chimney typically allows for a proper draft that helps with fuel efficiency and safe operation of combustion appliances. Therefore, understanding the risks associated with a blocked chimney is crucial for maintaining safety in environments using combustion appliances.