Testing Local Ventilation Systems (Module 6)

Question 1

What do we hope to accomplish when testing LEV systems?

Answer 1

• Determining effectiveness of LEV system
• Establishing baseline conditions for the LEV system
• Monitoring conditions throughout the life of the system
• Evaluating changes made to the system

Question 2

Where do we take ventilation measurements?

Answer 2

1. at the face of booth type hoods
2. just downstream of a hood at a branch location
3. in the main to define hood exhaust rate by difference
4. in the main duct to define total system airflow

Question 3

What techniques are most suitable for evaluating LV?

Answer 3

Qualitative & quantative

Question 4

What is quantitative?

Answer 4

• Measuring velocity profile (anemometers)
• Measuring pressure (Pitot tubes, manometers)
• Physical measurements (duct diameter and circumference, elbow R/D, hood dimensions)

Question 5

What is qualitative?

Answer 5

• Observing direction and strength of airflow (smoke tubes, smoke bombs)

Question 6

What is smoke visualization?

Answer 6

• Smoke tube” is opened
• Stannic chloride dust cloud is released from a tube
• Tube held in a number of locations in front of a hood-to determine the location of the hood’s zone of capture
• Can estimate air velocity by distance travelled by smoke/Time of travel

Question 7

What kind of test is smoke visualization?

Answer 7

qualitative

Question 8

What kind of test are helium filled bubbles?

Answer 8

qualitative