If substantial changes are made to the ventilation system in a place where the mine's air quality and flow have to be measured, when must the flow rate be measured?

• A. Before the change
• B. Immediately after the change
• C. After 1 day
• D. At next shift

Answer: (B)

When substantial changes are made to a ventilation system that affect air quality and flow, you verify the new setup right away. Measuring the flow rate immediately after the change establishes a current baseline and confirms the new configuration meets required ventilation performance before any work continues. Waiting until later—after one day or the next shift—allows conditions to drift as fans ramp up or down, dampers settle, doors move, or people enter the area, which can mask issues or give a misleading view of the system’s true capability. Measuring before the change wouldn’t reflect the updated setup, so it wouldn’t prove the new ventilation performance.