CA D-90 Air Duct Cleaning Contractor Exam
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A|
Instant Download Pdf
1. What is the primary purpose of cleaning an HVAC air-distribution
system?
A. Increase the refrigerant charge
B. Remove accumulated dust, debris, and contaminants from system
components
C. Replace all supply registers
D. Increase the thermostat setting
Answer: B. Remove accumulated dust, debris, and contaminants from
system components
Rationale: Air-duct cleaning is intended to remove accumulated
particulate matter and other contaminants from accessible HVAC
system components. Proper cleaning can improve system cleanliness
,and help prevent accumulated debris from being redistributed
through the building.
2. Before beginning an air-duct cleaning project, what should the
contractor do first?
A. Start the vacuum equipment
B. Remove all supply registers
C. Inspect and assess the HVAC system and work area
D. Apply chemical treatment throughout the ductwork
Answer: C. Inspect and assess the HVAC system and work area
Rationale: A preliminary inspection establishes the condition of the
duct system, identifies contamination, determines access
requirements, and helps the contractor select appropriate equipment
and procedures. Starting work without an assessment can result in
incomplete cleaning or unnecessary damage.
3. Which component is commonly found inside an HVAC air-
distribution system?
A. Supply and return ducts
B. Domestic water heater only
C. Natural gas meter
D. Plumbing drain trap
,Answer: A. Supply and return ducts
Rationale: HVAC air-distribution systems typically include supply
ducts, return ducts, air handlers, grilles, registers, diffusers, and
related components. These components must be considered when
planning a comprehensive cleaning.
4. What is the main purpose of negative pressure during duct
cleaning?
A. To heat the ductwork
B. To prevent contaminants from escaping into occupied areas
C. To increase indoor humidity
D. To reduce electrical consumption
Answer: B. To prevent contaminants from escaping into occupied
areas
Rationale: Negative pressure helps control the movement of
contaminated air toward the collection equipment rather than
allowing loosened particles to migrate into the building. Maintaining
appropriate containment is an important part of protecting occupants
and nearby areas.
5. Which piece of equipment is commonly used to collect loosened
duct contaminants?
, A. Air compressor only
B. Vacuum collection system
C. Water softener
D. Refrigerant recovery cylinder
Answer: B. Vacuum collection system
Rationale: Vacuum collection equipment creates controlled airflow
that transports loosened contaminants from the duct system into a
collection device. The equipment should be appropriately sized and
configured for the system being cleaned.
6. Why should supply and return openings be controlled during duct
cleaning?
A. To prevent unwanted airflow and migration of contaminants
B. To increase refrigerant pressure
C. To make the thermostat operate faster
D. To eliminate the need for inspection
Answer: A. To prevent unwanted airflow and migration of
contaminants
Rationale: Uncontrolled openings can allow contaminated air or
debris to move into areas that are not being cleaned. Properly sealing
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A|
Instant Download Pdf
1. What is the primary purpose of cleaning an HVAC air-distribution
system?
A. Increase the refrigerant charge
B. Remove accumulated dust, debris, and contaminants from system
components
C. Replace all supply registers
D. Increase the thermostat setting
Answer: B. Remove accumulated dust, debris, and contaminants from
system components
Rationale: Air-duct cleaning is intended to remove accumulated
particulate matter and other contaminants from accessible HVAC
system components. Proper cleaning can improve system cleanliness
,and help prevent accumulated debris from being redistributed
through the building.
2. Before beginning an air-duct cleaning project, what should the
contractor do first?
A. Start the vacuum equipment
B. Remove all supply registers
C. Inspect and assess the HVAC system and work area
D. Apply chemical treatment throughout the ductwork
Answer: C. Inspect and assess the HVAC system and work area
Rationale: A preliminary inspection establishes the condition of the
duct system, identifies contamination, determines access
requirements, and helps the contractor select appropriate equipment
and procedures. Starting work without an assessment can result in
incomplete cleaning or unnecessary damage.
3. Which component is commonly found inside an HVAC air-
distribution system?
A. Supply and return ducts
B. Domestic water heater only
C. Natural gas meter
D. Plumbing drain trap
,Answer: A. Supply and return ducts
Rationale: HVAC air-distribution systems typically include supply
ducts, return ducts, air handlers, grilles, registers, diffusers, and
related components. These components must be considered when
planning a comprehensive cleaning.
4. What is the main purpose of negative pressure during duct
cleaning?
A. To heat the ductwork
B. To prevent contaminants from escaping into occupied areas
C. To increase indoor humidity
D. To reduce electrical consumption
Answer: B. To prevent contaminants from escaping into occupied
areas
Rationale: Negative pressure helps control the movement of
contaminated air toward the collection equipment rather than
allowing loosened particles to migrate into the building. Maintaining
appropriate containment is an important part of protecting occupants
and nearby areas.
5. Which piece of equipment is commonly used to collect loosened
duct contaminants?
, A. Air compressor only
B. Vacuum collection system
C. Water softener
D. Refrigerant recovery cylinder
Answer: B. Vacuum collection system
Rationale: Vacuum collection equipment creates controlled airflow
that transports loosened contaminants from the duct system into a
collection device. The equipment should be appropriately sized and
configured for the system being cleaned.
6. Why should supply and return openings be controlled during duct
cleaning?
A. To prevent unwanted airflow and migration of contaminants
B. To increase refrigerant pressure
C. To make the thermostat operate faster
D. To eliminate the need for inspection
Answer: A. To prevent unwanted airflow and migration of
contaminants
Rationale: Uncontrolled openings can allow contaminated air or
debris to move into areas that are not being cleaned. Properly sealing
