Final answer:
With both BLOWER and EXTRACT PB's in OVRD, manual control is engaged, with the INLET and EXTRACT valves typically open or set to specific positions, depending on the system's design and safety protocols.
Step-by-step explanation:
When both the BLOWER and EXTRACT PB's (push buttons) are in OVRD (override) position, it generally indicates that manual control over the ventilation system has been engaged, bypassing automatic controls. The specific positions of the INLET and EXTRACT valves would depend on the control logic or safety protocols of the particular system. However, in a typical scenario in HVAC (Heating, Ventilation, and Air Conditioning) or industrial systems, when in override mode, the INLET valve may be either fully open or set to a predetermined position to facilitate airflow. Similarly, the EXTRACT valve could also be fully open or set to maintain a specific level of extraction independent of the system's sensors or automatic settings.