NCT Air Filtration Fundamentals & Filter Media 1 — Questions and Answers
Question 1: What does MERV stand for in air filtration?
- Maximum Efficiency Reporting Value (Correct answer)
- Minimum Energy Recovery Ventilation
- Measured Efficiency Rating Volume
- Minimum Environmental Regulation Value
Correct answer: Maximum Efficiency Reporting Value
MERV stands for Minimum Efficiency Reporting Value, the ASHRAE standard rating system for air filter efficiency.
Question 2: Which MERV rating range is typically used for commercial buildings requiring superior particulate control?
- MERV 1–4
- MERV 5–8
- MERV 9–12
- MERV 13–16 (Correct answer)
Correct answer: MERV 13–16
MERV 13–16 filters capture fine particles including bacteria and smoke and are used in commercial settings requiring superior air quality.
Question 3: A HEPA filter must capture what minimum percentage of particles at 0.3 microns?
- 95%
- 97%
- 99.97% (Correct answer)
- 99.50%
Correct answer: 99.97%
By definition, a true HEPA filter must capture at least 99.97% of particles at the most penetrating particle size of 0.3 microns.
Question 4: Which particle size is considered the Most Penetrating Particle Size (MPPS) for standard air filtration media?
- 10 microns
- 5 microns
- 0.3 microns (Correct answer)
- 1 micron
Correct answer: 0.3 microns
0.3 microns is the MPPS because particles of this size are too large to follow airstream diffusion yet too small for effective inertial impaction.
Question 5: What filtration mechanism primarily captures large particles (>1 micron) through direct contact with filter fibers?
- Diffusion
- Electrostatic attraction
- Inertial impaction (Correct answer)
- Interception
Correct answer: Inertial impaction
Inertial impaction occurs when large particles cannot follow the airstream around a fiber and collide directly with it.
Question 6: Arrestance, as used in air filter testing, measures the filter's ability to capture which type of test dust?
- Fine atmospheric dust
- ASHRAE standard synthetic test dust (Correct answer)
- Diesel exhaust particulate
- Pollen and mold spores
Correct answer: ASHRAE standard synthetic test dust
Arrestance is measured using ASHRAE standard synthetic test dust to evaluate a filter's overall mass-based capture efficiency.
Question 7: Which filter type uses a charged medium to enhance particle capture without significantly increasing resistance to airflow?
- Fiberglass panel filter
- Electret filter (Correct answer)
- Activated carbon filter
- ULPA filter
Correct answer: Electret filter
Electret filters use permanently charged synthetic fibers that attract particles electrostatically, boosting efficiency at low pressure drop.
NCT Air Filtration Fundamentals & Filter Media 1
What does MERV stand for in air filtration?