$29.$ The formula is:

$Q=AV$

$Q($flow volume rate, cubic feet per minute $($CFM$)=A($area of entry point in ft$.)$ X V $($velocity of air entering space, feet per minute, $($FPM$)$

The diameter of the opening is $3$ ft and the measured face velocity entering the space is $750$ fpm $.$ What is the CFM entering space?

$30.$ What does Hierarchy of Controls mean?

$31.$ You are walking a unit being cleared maintenance work, you detect an elevated reading. What would you do$?$