NAFA CERTIFIED AIR FILTER SPECIALIST (CAFS) ACTUAL
EXAM 2026/2027 AND STUDY GUIDE ACCURATE TEST
COMPLETE REAL QUESTIONS WITH WELL ELABORATED
ANSWERS WITH DETAILED RATIONALES (VERIFIED
SOLUTIONS) A NEW UPDATED VERSION 2026 EDITION
|GUARANTEED PASS A+ (BRAND NEW!) |INSTANT PDF
1. Which of the following best defines the primary purpose of an air
filter in a forced-air HVAC system?
A. To remove gaseous pollutants from the airstream
B. To control humidity levels within the occupied space
C. To protect equipment and improve indoor air quality by
removing particulate matter
D. To add thermal energy to the supply air
Correct Answer: C. To protect equipment and improve indoor air
quality by removing particulate matter
Rationale: The primary purpose of an air filter is to capture airborne
particulates to prevent them from depositing on HVAC components
(coils, ducts, fans) and to reduce occupant exposure to particulates. Gas
removal and humidity control require separate devices.
2. According to ASHRAE Standard 52.2, the removal efficiency of an
air filter is expressed as:
A. Minimum Efficiency Reporting Value (MERV)
B. Arrestance
C. Dust Spot Efficiency
D. Pressure Drop
Correct Answer: A. Minimum Efficiency Reporting Value (MERV)
Rationale: ASHRAE Standard 52.2 establishes the MERV scale (1–20)
,based on particle size removal efficiency (0.3–10 am). Arrestance relates
to ASHRAE 52.1 for synthetic dust, and dust spot efficiency is an older
metric.
3. A filter with a MERV 14 rating is most effective at capturing which
particle size range?
A. >10 am
B. 3–10 am
C. 0.3–1.0 am
D. <0.1 am
Correct Answer: C. 0.3–1.0 am
Rationale: MERV 14 indicates ≥75% efficiency for 0.3–1.0 am
particles and ≥90% for 1–3 am, making it suitable for fine particulates
like bacteria, tobacco smoke, and many combustion byproducts.
4. Which test method provides a filter’s initial resistance at a specified
airflow?
A. ASHRAE 52.1 Dust Arrestance
B. ASHRAE 52.2
C. ISO 16890
D. ASHRAE 62.1
Correct Answer: B. ASHRAE 52.2
Rationale: ASHRAE Standard 52.2 includes measurement of initial
resistance (pressure drop) across the filter at rated airflow. While ISO
16890 is used internationally, the CAFS exam references ASHRAE 52.2
for MERV and resistance.
5. A minimum efficiency reporting value (MERV) of 8 corresponds to
which typical application?
A. Cleanrooms and pharmaceutical manufacturing
B. Commercial buildings, better residential filters
C. Pain booths and welding fume extraction
,D. Hospital operating rooms
Correct Answer: B. Commercial buildings, better residential filters
Rationale: MERV 8–11 is common for commercial HVAC and
premium residential systems, offering good capture of pollen, dust
mites, and mold spores. MERV 14+ is for cleanrooms, and MERV 16+
for operating rooms.
6. If a filter’s pressure drop doubles while airflow remains constant, the
energy consumption of the fan will approximately:
A. Remain the same
B. Decrease by half
C. Double
D. Increase four times
Correct Answer: C. Double
Rationale: Fan power is proportional to pressure drop × airflow.
Constant airflow means doubling pressure drop doubles the required
power, increasing operating cost.
7. Which factor has the largest influence on the initial efficiency of a
new pleated filter?
A. Relative humidity
B. Media pore size and structure
C. Filter frame color
D. Duct material
Correct Answer: B. Media pore size and structure
Rationale: The physical characteristics of the filter media (fiber
diameter, density, thickness) determine the initial particle capture
mechanisms—impaction, interception, and diffusion.
8. A filter’s arrestance according to ASHRAE 52.1 measures:
A. Removal efficiency of 0.3–1.0 am particles
B. Ability to capture coarse test dust (by weight)
, C. Filter structural integrity
D. Resistance to moisture
Correct Answer: B. Ability to capture coarse test dust (by weight)
Rationale: Arrestance is the percentage of standard ASHRAE synthetic
test dust (coarse, large particles) removed by weight, used for low-
efficiency filters like MERV 1–4.
9. What is the typical recommended final pressure drop (change-out
point) for a bag filter in commercial HVAC?
A. 0.2 inches wag. above initial
B. 1.0 to 1.5 inches wag. above initial
C. 3.0 inches wag. above initial
D. No change — replace only when visually dirty
Correct Answer: B. 1.0 to 1.5 inches wag. above initial
Rationale: Most bag filters (MERV 8–15) are changed when resistance
reaches 1.0–1.5” wag. over initial to balance energy cost vs. filter life.
Higher drops increase fan energy and risk collapse.
10. A HEPA filter, as defined by DOE standards, must have minimum
efficiency of:
A. 85% on 0.3 am particles
B. 95% on 0.3 am particles
C. 99.97% on 0.3 am particles
D. 99.999% on 0.1 am particles
Correct Answer: C. 99.97% on 0.3 am particles
Rationale: The U.S. DOE standard requires HEPA filters to achieve
≥99.97% efficiency for 0.3 am particles—the most penetrating particle
size (MPPS) for HEPA media.
11. ULPA (Ultra-Low Penetration Air) filters typically have efficiency
of:
A. 95% at 0.3 am
EXAM 2026/2027 AND STUDY GUIDE ACCURATE TEST
COMPLETE REAL QUESTIONS WITH WELL ELABORATED
ANSWERS WITH DETAILED RATIONALES (VERIFIED
SOLUTIONS) A NEW UPDATED VERSION 2026 EDITION
|GUARANTEED PASS A+ (BRAND NEW!) |INSTANT PDF
1. Which of the following best defines the primary purpose of an air
filter in a forced-air HVAC system?
A. To remove gaseous pollutants from the airstream
B. To control humidity levels within the occupied space
C. To protect equipment and improve indoor air quality by
removing particulate matter
D. To add thermal energy to the supply air
Correct Answer: C. To protect equipment and improve indoor air
quality by removing particulate matter
Rationale: The primary purpose of an air filter is to capture airborne
particulates to prevent them from depositing on HVAC components
(coils, ducts, fans) and to reduce occupant exposure to particulates. Gas
removal and humidity control require separate devices.
2. According to ASHRAE Standard 52.2, the removal efficiency of an
air filter is expressed as:
A. Minimum Efficiency Reporting Value (MERV)
B. Arrestance
C. Dust Spot Efficiency
D. Pressure Drop
Correct Answer: A. Minimum Efficiency Reporting Value (MERV)
Rationale: ASHRAE Standard 52.2 establishes the MERV scale (1–20)
,based on particle size removal efficiency (0.3–10 am). Arrestance relates
to ASHRAE 52.1 for synthetic dust, and dust spot efficiency is an older
metric.
3. A filter with a MERV 14 rating is most effective at capturing which
particle size range?
A. >10 am
B. 3–10 am
C. 0.3–1.0 am
D. <0.1 am
Correct Answer: C. 0.3–1.0 am
Rationale: MERV 14 indicates ≥75% efficiency for 0.3–1.0 am
particles and ≥90% for 1–3 am, making it suitable for fine particulates
like bacteria, tobacco smoke, and many combustion byproducts.
4. Which test method provides a filter’s initial resistance at a specified
airflow?
A. ASHRAE 52.1 Dust Arrestance
B. ASHRAE 52.2
C. ISO 16890
D. ASHRAE 62.1
Correct Answer: B. ASHRAE 52.2
Rationale: ASHRAE Standard 52.2 includes measurement of initial
resistance (pressure drop) across the filter at rated airflow. While ISO
16890 is used internationally, the CAFS exam references ASHRAE 52.2
for MERV and resistance.
5. A minimum efficiency reporting value (MERV) of 8 corresponds to
which typical application?
A. Cleanrooms and pharmaceutical manufacturing
B. Commercial buildings, better residential filters
C. Pain booths and welding fume extraction
,D. Hospital operating rooms
Correct Answer: B. Commercial buildings, better residential filters
Rationale: MERV 8–11 is common for commercial HVAC and
premium residential systems, offering good capture of pollen, dust
mites, and mold spores. MERV 14+ is for cleanrooms, and MERV 16+
for operating rooms.
6. If a filter’s pressure drop doubles while airflow remains constant, the
energy consumption of the fan will approximately:
A. Remain the same
B. Decrease by half
C. Double
D. Increase four times
Correct Answer: C. Double
Rationale: Fan power is proportional to pressure drop × airflow.
Constant airflow means doubling pressure drop doubles the required
power, increasing operating cost.
7. Which factor has the largest influence on the initial efficiency of a
new pleated filter?
A. Relative humidity
B. Media pore size and structure
C. Filter frame color
D. Duct material
Correct Answer: B. Media pore size and structure
Rationale: The physical characteristics of the filter media (fiber
diameter, density, thickness) determine the initial particle capture
mechanisms—impaction, interception, and diffusion.
8. A filter’s arrestance according to ASHRAE 52.1 measures:
A. Removal efficiency of 0.3–1.0 am particles
B. Ability to capture coarse test dust (by weight)
, C. Filter structural integrity
D. Resistance to moisture
Correct Answer: B. Ability to capture coarse test dust (by weight)
Rationale: Arrestance is the percentage of standard ASHRAE synthetic
test dust (coarse, large particles) removed by weight, used for low-
efficiency filters like MERV 1–4.
9. What is the typical recommended final pressure drop (change-out
point) for a bag filter in commercial HVAC?
A. 0.2 inches wag. above initial
B. 1.0 to 1.5 inches wag. above initial
C. 3.0 inches wag. above initial
D. No change — replace only when visually dirty
Correct Answer: B. 1.0 to 1.5 inches wag. above initial
Rationale: Most bag filters (MERV 8–15) are changed when resistance
reaches 1.0–1.5” wag. over initial to balance energy cost vs. filter life.
Higher drops increase fan energy and risk collapse.
10. A HEPA filter, as defined by DOE standards, must have minimum
efficiency of:
A. 85% on 0.3 am particles
B. 95% on 0.3 am particles
C. 99.97% on 0.3 am particles
D. 99.999% on 0.1 am particles
Correct Answer: C. 99.97% on 0.3 am particles
Rationale: The U.S. DOE standard requires HEPA filters to achieve
≥99.97% efficiency for 0.3 am particles—the most penetrating particle
size (MPPS) for HEPA media.
11. ULPA (Ultra-Low Penetration Air) filters typically have efficiency
of:
A. 95% at 0.3 am
