Airflow switch or transducer shall open the interlock circuit when the airflow falls to what percentage of the listed rating?

Airflow switch or transducer shall open the interlock circuit when the airflow falls to what percentage of the listed rating?

• A. 25% or 10% of the listed rating
• B. 50% of the listed rating
• C. 75% of the listed rating
• D. 5% of the listed rating

Answer: (A)

Airflow sensing devices protect the interlock by turning it open whenever the ventilation is no longer providing adequate flow. The interlock is designed to respond when the actual airflow drops to a small fraction of what the system is rated for—typically around a quarter of the listed rating, and in some listings as low as about one-tenth. This ensures that if the hood’s fan slows, a damper closes, or airflow is otherwise reduced, the control state changes to a safe condition and prevents unsafe operation or improper discharge. Using a fraction of the rated airflow accounts for normal variations and tolerances, while avoiding letting the system continue to operate under poor ventilation. Therefore, the threshold being 25% or 10% of the listed rating, depending on the specific device, is the correct concept.

Airflow sensing devices protect the interlock by turning it open whenever the ventilation is no longer providing adequate flow. The interlock is designed to respond when the actual airflow drops to a small fraction of what the system is rated for—typically around a quarter of the listed rating, and in some listings as low as about one-tenth. This ensures that if the hood’s fan slows, a damper closes, or airflow is otherwise reduced, the control state changes to a safe condition and prevents unsafe operation or improper discharge. Using a fraction of the rated airflow accounts for normal variations and tolerances, while avoiding letting the system continue to operate under poor ventilation. Therefore, the threshold being 25% or 10% of the listed rating, depending on the specific device, is the correct concept.