Air Filtration Fundamentals & Filter Media Flashcards

What does MERV stand for in air filtration?

Answer: Maximum Efficiency Reporting Value

MERV stands for Minimum Efficiency Reporting Value, the ASHRAE standard rating system for air filter efficiency.

Which MERV rating range is typically used for commercial buildings requiring superior particulate control?

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.

A HEPA filter must capture what minimum percentage of particles at 0.3 microns?

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.

Which particle size is considered the Most Penetrating Particle Size (MPPS) for standard air filtration media?

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.

What filtration mechanism primarily captures large particles (>1 micron) through direct contact with filter fibers?

Answer: Inertial impaction

Inertial impaction occurs when large particles cannot follow the airstream around a fiber and collide directly with it.

Arrestance, as used in air filter testing, measures the filter's ability to capture which type of test dust?

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.

Which filter type uses a charged medium to enhance particle capture without significantly increasing resistance to airflow?

Answer: Electret filter

Electret filters use permanently charged synthetic fibers that attract particles electrostatically, boosting efficiency at low pressure drop.