Exceptions for chimneys used with __________ chamber fireplaces require compliance with UL 103 regulations.

Chimneys used with open combustion chamber fireplaces must comply with UL 103 regulations because these regulations set the standards for the safety and performance of chimney systems connected to appliances that draw combustion air from the indoor environment. Open combustion fireplaces typically utilize ambient air for combustion, meaning they can pose greater risks related to efficiency and venting. As a result, the UL 103 standard ensures that the chimney can handle the byproducts of combustion and maintain proper draft while minimizing the risks of fire and other hazards. These regulations cover aspects such as material specifications, construction methods, and testing requirements to ensure safety in these systems.

The complexities of venting and combustion efficiency in open combustion setups necessitate strict adherence to safety standards, which is why compliance with UL 103 is emphasized in their construction and installation.