What requirement is necessary for vehicles equipped with a CNG fuel system?

For vehicles equipped with a CNG fuel system, one of the critical requirements is the presence of a durable label that is readily visible and located at the fueling connection receptacle. This label serves an essential function: it provides vital information about the CNG fuel system, including safety warnings, operational guidelines, and proper handling procedures. This ensures that both users and emergency responders are informed about the specifics of the CNG system, which is important for safe fueling and maintenance practices. Having clear identification at the fueling point enhances safety and facilitates proper management of the fuel system.

The other options, while important for vehicle safety and functionality in different contexts, do not specifically address the requirements set forth for CNG fuel systems. For instance, airbags and engine oil types pertain more to general vehicle safety and maintenance standards rather than CNG-specific requirements. Similarly, vehicle age could relate to overall regulations but does not uniquely pertain to the specifications of CNG fuel systems. Thus, the presence of a durable label at the fueling connection is the most relevant requirement for CNG-equipped vehicles.