Which of the following is NOT a requirement of NFPA 54?

The choice indicating that safety checks must be conducted regularly is not a specific requirement of NFPA 54. NFPA 54, also known as the National Fuel Gas Code, outlines safety criteria for gas systems and appliances, focusing primarily on the installation and maintenance of gas appliances, including fuel gas piping and venting systems.

In contrast, the other options relate directly to key requirements outlined in the code. Combustion air provision for large input levels ensures that sufficient air supply is available for proper appliance operation, preventing unsafe combustion conditions. Gas supply odorization is a safety feature mandated to help detect gas leaks through the odorized compounds added to natural gas. Additionally, ensuring that all combustion zones have adequate ventilation is crucial to maintain safe and effective appliance operation, preventing the buildup of harmful gases.

Thus, while regular safety checks are important for overall appliance safety and are often part of industry best practices or may be required by other regulations, they are not explicitly mandated by NFPA 54 itself.