The minimum hood induced air velocity necessary to capture and transport the contaminant

The minimum hood induced air velocity necessary to capture and transport the contaminant

• A. Capture Velocity
• B. Face Velocity
• C. Air Changes Per Hour (ACH)
• D. Illuminance

Answer: (A)

Capturing contaminants with a hood relies on creating an inward pull at the opening strong enough to seize the plume as it’s emitted. The minimum air velocity at the hood face that achieves this capture is called the capture velocity. It’s the threshold value the hood must reach to pull the contaminant into the exhaust stream and transport it away, rather than allowing it to drift into the surrounding room. Face velocity, by contrast, is simply the average air speed across the entire hood opening. It describes how fast air is moving at the opening, but it doesn’t specify the critical speed needed to actually capture and entrain the plume. ACH relates to the overall room ventilation rate, not the hood’s ability to capture a specific emission. Illuminance is about lighting, which isn't involved in contaminant capture.

Capturing contaminants with a hood relies on creating an inward pull at the opening strong enough to seize the plume as it’s emitted. The minimum air velocity at the hood face that achieves this capture is called the capture velocity. It’s the threshold value the hood must reach to pull the contaminant into the exhaust stream and transport it away, rather than allowing it to drift into the surrounding room.

Face velocity, by contrast, is simply the average air speed across the entire hood opening. It describes how fast air is moving at the opening, but it doesn’t specify the critical speed needed to actually capture and entrain the plume. ACH relates to the overall room ventilation rate, not the hood’s ability to capture a specific emission. Illuminance is about lighting, which isn't involved in contaminant capture.