What is a simple method to evaluate a local exhaust ventilation system performance?

• A. It cannot be evaluated easily.
• B. Visual inspection is enough.
• C. Measure only the exhaust temperature.
• D. Compare actual capture velocity and face velocity against design values and perform airflow testing.

Answer: (D)

The main idea here is to verify that a local exhaust ventilation system is actually pulling contaminants in as designed, not just looking like it’s working. The best way to do that is to perform airflow testing and compare what you measure to what the system was designed for. Specifically, you measure the actual capture velocity at the hood opening and the face velocity across the hood, along with the total exhaust airflow, and then compare those values to the design targets. If the measured velocities and flow match the design values, you can be confident the system should capture contaminants effectively in practice.

Why this approach is better than the others: visual checks only assess how things look, not how air is moving, so they can miss leaks, obstructions, or imbalances that reduce performance. Measuring only exhaust temperature tells you about heat but not about airflow or capture efficiency. Quantitative airflow testing, by contrast, directly assesses the key performance indicators—capture and face velocities and total flow—so you know whether the system will actually contain emissions as intended.