What type of obstruction is mentioned in relation to underfloor passages for appliances?

Underfloor passages for appliances must have unobstructed flow to ensure proper functioning and safety. This means that the passageways should not have any physical barriers or obstructions that would impede the movement of air or the installation and maintenance of the appliances. Unobstructed flow is crucial as it allows for the free circulation of air, which is essential for ventilating appliances that generate heat or require combustion air.

In contrast to unobstructed flow, options related to airflow restrictions, obstructed flow, or limited access imply the presence of barriers or hindrances that could interfere with the efficiency and safety of the appliance operation. This reinforces the importance of maintaining clear pathways in underfloor spaces to support both effective appliance performance and compliance with safety codes. Such clearances not only facilitate airflow but also ease access for maintenance purposes, thereby promoting the overall functionality of the mechanical system.