NAFA CAFS TEST EXAM FULLY SOLVED & UPDATED 2026(LATEST VERSION
VERIFIED FOR ACCURACY)/NEWEST
Question 1
A micron is a unit of measure used in the filtration industry to describe particle size. One micron
is approximately what fraction of an inch?
A) 1/1,000"
B) 1/10,000"
C) 1/25,400"
D) 1/50,000"
E) 1/100,000"
Correct Answer: C) 1/25,400"
Rationale: According to the NAFA Guide, a micron is defined as one-millionth of a meter.
When converted to the imperial system used in the United States, there are approximately
25,400 microns in a single inch.
Question 2
Particle counters are essential for measuring indoor air quality. While older units used tungsten
light and were limited to 0.3 microns, newer units use what light source to detect particles
smaller than 0.1 micron?
A) Halogen
B) Ultraviolet
C) Infrared
D) Lasers
E) LED
Correct Answer: D) Lasers
Rationale: The introduction of laser technology in particle counters allowed for a more
concentrated and precise light source, enabling the detection and counting of sub-micron
particles down to levels below 0.1 microns.
Question 3
What is the formula used to calculate the media velocity (fpm) of air passing through a filter?
A) Velocity = CFM × Square feet of media
B) Velocity = CFM / Square feet of media
C) Velocity = CFM + Face Area
D) Velocity = Static Pressure / CFM
E) Velocity = (Face Area / Media Area) × 100
Correct Answer: B) Velocity = CFM / Square feet of media
Rationale: Velocity (fpm) is determined by dividing the air volume flow rate (Q in cfm) by
the area of the filter media (A in square feet). This is expressed as V = Q/A.
Question 4
If a 20x24x12 filter contains 48 square feet of media and is placed in an airstream of 2,000 cfm,
what is the media velocity?
, 2
A) 250 fpm
B) 100 fpm
C) 41.66 fpm
D) 50.25 fpm
E) 12.5 fpm
Correct Answer: C) 41.66 fpm
Rationale: Using the formula V = Q/A, we take the air volume of 2,000 cfm and divide it by
the 48 sq. ft. of media. = 41.66 fpm.
Question 5
Which of the following describes an "Extended Surface Filter"?
A) A filter that is 12 inches deep or more.
B) A filter in which the media area is greater than the face area.
C) A filter that uses an external power source.
D) A filter designed to be washed and reused.
E) A filter that occupies the entire width of the duct.
Correct Answer: B) A filter in which the media area is greater than the face area.
Rationale: Extended surface filters (such as pleated filters or bag filters) increase the
surface area of the media relative to the opening (face) of the filter. This results in a media
velocity that is significantly lower than the face velocity.
Question 6
The probability of a particle colliding with a fiber in the filter media increases under which of the
following conditions?
A) The fibers are oriented further apart.
B) The filter media is thinner.
C) The air velocity is increased to maximum.
D) The filter media is thicker and fibers are oriented more closely.
E) The particles are smaller than 0.01 microns.
Correct Answer: D) The filter media is thicker and fibers are oriented more closely.
Rationale: Collision probability is a function of density and depth. Thicker media and
tighter fiber orientation create a more complex "obstacle course" for particles, increasing
the likelihood of interception or impingement.
Question 7
Impingement filters are frequently treated with what substance to create a bond between the
particle and the fiber?
A) Water-based coolants
B) Adhesives (tackifiers)
C) Conductive carbon
D) Fire retardant spray
, 3
E) Anti-microbial powder
Correct Answer: B) Adhesives (tackifiers)
Rationale: Adhesives or tackifiers are used to coat the fibers in impingement filters. When a
particle strikes a fiber, the adhesive ensures it "sticks" and is not re-entrained into the
airstream.
Question 8
In air filtration physics, when is the strongest attraction force observed between particles and
fibers?
A) When the particle is twice the size of the fiber.
B) When the air is highly humid.
C) When particles and fibers are approximately the same diameter.
D) When the air velocity is at its lowest point.
E) When the filter is brand new and has no dust load.
Correct Answer: C) When particles and fibers are approximately the same diameter.
Rationale: Studies in filtration mechanics show that the most effective capture via van der
Waals forces and electrostatic attraction occurs when the target (fiber) and the pollutant
(particle) have similar physical dimensions.
Question 9
How is "Dust Holding Capacity" defined in the filtration industry?
A) The total weight of the filter after one year of use.
B) The amount of dust retained by a filter until it reaches its final recommended pressure drop.
C) The number of particles caught per square inch.
D) The maximum amount of dust a filter can hold before the media tears.
E) The amount of dust a filter holds at 50% efficiency.
Correct Answer: B) The amount of dust retained by a filter until it reaches its final
recommended pressure drop.
Rationale: Dust holding capacity is a measure of service life. It quantifies how much mass a
filter can capture before the resistance (pressure drop) becomes too high for the system to
operate efficiently.
Question 10
A "dipole moment" in molecular filtration refers to:
A) Two filters placed in a series.
B) A greater concentration of electrons at one end of a molecule than the other.
C) The moment a filter fails a DOP test.
D) The vibration caused by a fan.
E) The magnetic pull of a metal mesh filter.
Correct Answer: B) A greater concentration of electrons at one end of a molecule than the
other.
VERIFIED FOR ACCURACY)/NEWEST
Question 1
A micron is a unit of measure used in the filtration industry to describe particle size. One micron
is approximately what fraction of an inch?
A) 1/1,000"
B) 1/10,000"
C) 1/25,400"
D) 1/50,000"
E) 1/100,000"
Correct Answer: C) 1/25,400"
Rationale: According to the NAFA Guide, a micron is defined as one-millionth of a meter.
When converted to the imperial system used in the United States, there are approximately
25,400 microns in a single inch.
Question 2
Particle counters are essential for measuring indoor air quality. While older units used tungsten
light and were limited to 0.3 microns, newer units use what light source to detect particles
smaller than 0.1 micron?
A) Halogen
B) Ultraviolet
C) Infrared
D) Lasers
E) LED
Correct Answer: D) Lasers
Rationale: The introduction of laser technology in particle counters allowed for a more
concentrated and precise light source, enabling the detection and counting of sub-micron
particles down to levels below 0.1 microns.
Question 3
What is the formula used to calculate the media velocity (fpm) of air passing through a filter?
A) Velocity = CFM × Square feet of media
B) Velocity = CFM / Square feet of media
C) Velocity = CFM + Face Area
D) Velocity = Static Pressure / CFM
E) Velocity = (Face Area / Media Area) × 100
Correct Answer: B) Velocity = CFM / Square feet of media
Rationale: Velocity (fpm) is determined by dividing the air volume flow rate (Q in cfm) by
the area of the filter media (A in square feet). This is expressed as V = Q/A.
Question 4
If a 20x24x12 filter contains 48 square feet of media and is placed in an airstream of 2,000 cfm,
what is the media velocity?
, 2
A) 250 fpm
B) 100 fpm
C) 41.66 fpm
D) 50.25 fpm
E) 12.5 fpm
Correct Answer: C) 41.66 fpm
Rationale: Using the formula V = Q/A, we take the air volume of 2,000 cfm and divide it by
the 48 sq. ft. of media. = 41.66 fpm.
Question 5
Which of the following describes an "Extended Surface Filter"?
A) A filter that is 12 inches deep or more.
B) A filter in which the media area is greater than the face area.
C) A filter that uses an external power source.
D) A filter designed to be washed and reused.
E) A filter that occupies the entire width of the duct.
Correct Answer: B) A filter in which the media area is greater than the face area.
Rationale: Extended surface filters (such as pleated filters or bag filters) increase the
surface area of the media relative to the opening (face) of the filter. This results in a media
velocity that is significantly lower than the face velocity.
Question 6
The probability of a particle colliding with a fiber in the filter media increases under which of the
following conditions?
A) The fibers are oriented further apart.
B) The filter media is thinner.
C) The air velocity is increased to maximum.
D) The filter media is thicker and fibers are oriented more closely.
E) The particles are smaller than 0.01 microns.
Correct Answer: D) The filter media is thicker and fibers are oriented more closely.
Rationale: Collision probability is a function of density and depth. Thicker media and
tighter fiber orientation create a more complex "obstacle course" for particles, increasing
the likelihood of interception or impingement.
Question 7
Impingement filters are frequently treated with what substance to create a bond between the
particle and the fiber?
A) Water-based coolants
B) Adhesives (tackifiers)
C) Conductive carbon
D) Fire retardant spray
, 3
E) Anti-microbial powder
Correct Answer: B) Adhesives (tackifiers)
Rationale: Adhesives or tackifiers are used to coat the fibers in impingement filters. When a
particle strikes a fiber, the adhesive ensures it "sticks" and is not re-entrained into the
airstream.
Question 8
In air filtration physics, when is the strongest attraction force observed between particles and
fibers?
A) When the particle is twice the size of the fiber.
B) When the air is highly humid.
C) When particles and fibers are approximately the same diameter.
D) When the air velocity is at its lowest point.
E) When the filter is brand new and has no dust load.
Correct Answer: C) When particles and fibers are approximately the same diameter.
Rationale: Studies in filtration mechanics show that the most effective capture via van der
Waals forces and electrostatic attraction occurs when the target (fiber) and the pollutant
(particle) have similar physical dimensions.
Question 9
How is "Dust Holding Capacity" defined in the filtration industry?
A) The total weight of the filter after one year of use.
B) The amount of dust retained by a filter until it reaches its final recommended pressure drop.
C) The number of particles caught per square inch.
D) The maximum amount of dust a filter can hold before the media tears.
E) The amount of dust a filter holds at 50% efficiency.
Correct Answer: B) The amount of dust retained by a filter until it reaches its final
recommended pressure drop.
Rationale: Dust holding capacity is a measure of service life. It quantifies how much mass a
filter can capture before the resistance (pressure drop) becomes too high for the system to
operate efficiently.
Question 10
A "dipole moment" in molecular filtration refers to:
A) Two filters placed in a series.
B) A greater concentration of electrons at one end of a molecule than the other.
C) The moment a filter fails a DOP test.
D) The vibration caused by a fan.
E) The magnetic pull of a metal mesh filter.
Correct Answer: B) A greater concentration of electrons at one end of a molecule than the
other.
