NCT Air Filtration Fundamentals & Filter Media 2 — Questions and Answers
Question 1: ASHRAE Standard 52.2 is used to evaluate air filter performance primarily by measuring:
- Energy consumption and airflow volume
- Particle size efficiency and dust holding capacity (Correct answer)
- Filter media tensile strength
- Carbon adsorption capacity
Correct answer: Particle size efficiency and dust holding capacity
ASHRAE 52.2 measures particle size efficiency across 12 particle size ranges and dust holding capacity to assign a MERV rating.
Question 2: What is the primary purpose of activated carbon in an air filter?
- Capturing sub-micron particles
- Adsorbing gaseous pollutants and odors (Correct answer)
- Increasing filter media strength
- Reducing static pressure drop
Correct answer: Adsorbing gaseous pollutants and odors
Activated carbon adsorbs volatile organic compounds (VOCs), odors, and other gaseous contaminants through its large porous surface area.
Question 3: As a filter loads with dust during service, what generally happens to both its efficiency and pressure drop?
- Efficiency increases; pressure drop decreases
- Efficiency decreases; pressure drop decreases
- Efficiency increases; pressure drop increases (Correct answer)
- Efficiency decreases; pressure drop stays constant
Correct answer: Efficiency increases; pressure drop increases
As dust accumulates on a filter, the dust cake acts as an additional filtration medium, increasing efficiency, while restricted airflow increases pressure drop.
Question 4: Which filter construction type offers the greatest filter media surface area within a compact housing frame?
- Flat panel filter
- V-bank (V-pleat) filter (Correct answer)
- Bag filter
- Cartridge filter with deep pleats
Correct answer: V-bank (V-pleat) filter
V-bank filters arrange multiple pleated packs in a V configuration, maximizing media area and dust holding capacity in a short housing depth.
Question 5: Fiberglass filter media is commonly used in low-MERV panel filters because it offers:
- High chemical resistance and moisture absorption
- Low cost, low resistance, and acceptable efficiency for coarse dust (Correct answer)
- Superior submicron particle capture
- Long service life with no pressure drop increase
Correct answer: Low cost, low resistance, and acceptable efficiency for coarse dust
Fiberglass media is inexpensive, provides low initial resistance, and effectively captures larger airborne particles in MERV 1–4 applications.
Question 6: The Dust Holding Capacity (DHC) of a filter is important because it directly affects the filter's:
- Initial particle capture efficiency
- Service life and replacement interval (Correct answer)
- MERV rating category
- Frame material selection
Correct answer: Service life and replacement interval
DHC measures how much synthetic dust a filter holds before reaching its terminal pressure drop, directly determining how long the filter lasts before replacement.
Question 7: In the context of NAFA certification, what does the term 'fractional efficiency' describe?
- The percentage of total airflow that bypasses the filter
- The efficiency of a filter at specific particle size intervals (Correct answer)
- The ratio of filter face area to total duct area
- The fraction of filter media that is active vs. inert
Correct answer: The efficiency of a filter at specific particle size intervals
Fractional efficiency specifies a filter's capture rate at defined particle size ranges, providing a detailed efficiency profile rather than a single overall number.
NCT Air Filtration Fundamentals & Filter Media 2
ASHRAE Standard 52.2 is used to evaluate air filter performance primarily by measuring: