Exam Questions And Correct Answers

CA D90 Air Duct Cleaning Contractor Exam Questions And Correct Answers (Verified Answers) Plus Rationale2026 Q&A| Instant Download Pdf

• What is the primary purpose of air duct cleaning?
• To improve HVAC system efficiency
• To eliminate all bacteria in a home
• To replace ductwork
• To insulate the ducts
• To improve HVAC system efficiency

Rationale: Cleaning air ducts removes dust and debris, improving

airflow and overall HVAC system efficiency.

• Which of the following is the most common contaminant found in air

ducts?

• Mold spores
• Dust and dirt
• Asbestos
• Lead
• Dust and dirt

Rationale: Dust, dirt, and small debris are the most common

materials that accumulate in ductwork over time.

• What safety equipment is essential for a technician during duct

cleaning?

• Safety glasses and gloves
• Hard hat only
• Steel-toed boots only
• Respirator, gloves, and eye protection
• Respirator, gloves, and eye protection 1 / 3

Rationale: Air duct cleaning can release dust, debris, and mold

spores, so proper PPE including a respirator is critical.

• Which method is commonly used to clean air ducts?
• Chemical injection
• High-powered vacuum and brushes
• Heat treatment
• Steam cleaning
• High-powered vacuum and brushes

Rationale: Professional duct cleaning typically uses high-powered

vacuums combined with rotary brushes to remove debris.

• How often should air ducts be professionally cleaned in a residential

setting?

• Every 6 months
• Every 3–5 years
• Once in a lifetime
• Every year
• Every 3–5 years

Rationale: The National Air Duct Cleaners Association recommends

cleaning every 3–5 years unless contamination is evident.

• Which type of HVAC system requires special care during duct cleaning

to prevent damage?

• Central forced-air systems
• High-velocity mini-duct systems
• Radiant heating systems
• Window AC units
• High-velocity mini-duct systems

Rationale: Mini-duct systems use smaller, more fragile ducts that can

be damaged by aggressive cleaning tools.

• What is a potential hazard when cleaning ducts with mold growth?
• Fire risk
• Electrical shock
• Health issues from spores
• Duct collapse
• Health issues from spores

Rationale: Mold spores can trigger respiratory problems, allergic

reactions, or infections if inhaled. 2 / 3

• Which of the following should be inspected before cleaning ducts?
• Duct material
• HVAC unit components
• Presence of leaks or holes
• All of the above
• All of the above

Rationale: Inspecting the system helps identify issues that could

affect cleaning or require repair before cleaning.

• What is the first step in a professional duct cleaning process?
• Apply chemical disinfectant
• Inspect and assess the system
• Seal all vents
• Vacuum the ducts
• Inspect and assess the system

Rationale: A thorough inspection ensures the cleaning process is

tailored to the system’s condition.

• Which of the following tools is specifically designed to agitate

debris inside ducts?

• Air compressor
• Rotating brush
• Steam nozzle
• Chemical sprayer
• Rotating brush

Rationale: Rotating brushes dislodge dirt and debris from duct walls

so it can be vacuumed out.

11. Negative air pressure during duct cleaning is used to:

• Prevent dust from escaping into living spaces
• Increase airflow to the HVAC unit
• Dry the ducts
• Kill bacteria
• Prevent dust from escaping into living spaces

Rationale: Negative pressure ensures debris and contaminants are

drawn into the vacuum system instead of escaping.

• Which is a sign that duct cleaning may be necessary?
• Visible dust on vent covers
• Persistent allergy symptoms
• Unpleasant odors from vents
• / 3