Which item is not permitted to be installed to maintain clearance from vent terminals?

Maintaining proper clearance from vent terminals is crucial for ensuring safe and effective operation of ventilation systems. Doorstops, while they might be used to hold doors open or prevent them from closing, can interfere with the function of vent terminals. If a doorstop is positioned too close to a vent terminal, it could obstruct airflow or create a situation where the vent terminal does not function as intended. This can lead to safety hazards, including negative pressure in the space, which may affect combustion appliances and could result in the accumulation of harmful gases.

On the other hand, hinges, closers, and locks are components that do not typically impede clearance from vent terminals. Hinges are necessary for the functioning of doors, and closers help ensure that doors close securely, which is important for maintaining building safety and integrity. Locks secure doors but do not contribute to obstruction in the same way doorstops can if misused. Therefore, it is doorstops that are specifically not permitted in proximity to vent terminals due to their potential to create clearance issues and compromise the safety and efficiency of the ventilation system.