Duct Cleaning Inspection Checklist

Per NADCA ACR 2013 (Assessment, Cleaning, and Restoration of HVAC Systems), inspect the duct system for conditions that warrant cleaning: visible mold growth on duct surfaces or components, excessive dust and debris accumulation, evidence of rodent or insect infestation, or verifiable contamination from construction or renovation. Use a borescope camera inspection at multiple points in the trunk line and branch runs to document conditions before cleaning. Not all duct systems need cleaning; only clean when specific contamination is confirmed.

1. Perform a visual inspection at supply and return registers by removing the covers and looking inside with a flashlight

2. Insert a borescope camera at access points to document conditions in the trunk line and branch ducts

3. Check for visible mold (dark staining with musty odor), excessive debris, rodent droppings, or insect evidence

4. Inspect the air handler, evaporator coil, and blower compartment for contamination

5. Document all findings with photos and video before any cleaning work begins

- Cleaning ducts that do not need it based on aggressive sales tactics (no contamination present)

- Missing mold growth that is hidden behind insulation lining inside the ducts

- Not inspecting the air handler and evaporator coil, which are often the dirtiest components

- Confusing normal dust accumulation with contamination that requires professional cleaning

Create access openings at trunk and branch line junctions if none exist, using a sheet metal cutter to make clean openings that can be sealed with access doors after cleaning. Seal all supply registers in rooms not being actively cleaned to maintain negative pressure in the system. Protect furnishings, flooring, and finishes with drop cloths in work areas. Connect the negative air machine (HEPA-filtered vacuum) to the main trunk line to capture all dislodged debris during cleaning.

1. Verify access points are created at all major junctions where trunk lines meet branch runs

2. Confirm all non-active registers are sealed with adhesive covers or magnetic covers to maintain system pressure

3. Check that drop cloths protect all flooring and furnishings within 6' of work areas

4. Verify the negative air machine is connected with a tight seal to the trunk line and is running before agitation begins

5. Confirm the HEPA filter in the negative air machine is properly seated and not bypassing

- Insufficient access points, leaving sections of ductwork uncleaned

- Not sealing unused registers, allowing debris to blow into occupied rooms during cleaning

- Negative air machine not connected before agitation begins, releasing debris into the living space

- Access doors not properly sealed after cleaning, creating air leaks in the duct system

Per NADCA standards, the source removal method is required: mechanical agitation (rotating brush, air whip, or compressed air nozzle) combined with a HEPA-filtered negative air machine to capture dislodged contaminants. Clean from the furthest duct run toward the negative air collection device. Each branch run must be individually cleaned. The entire supply side and return side must both be cleaned, along with the air handler, blower, evaporator coil, and drain pan. Do not use chemical sealants or encapsulants as a substitute for source removal cleaning.

1. Verify the contractor is using source removal (mechanical agitation + HEPA vacuum), not just blowing air through the ducts

2. Confirm each branch run is cleaned individually, not just the main trunk line

3. Check that both supply and return sides of the system are cleaned

4. Verify the air handler components (blower, evaporator coil, drain pan) are cleaned

5. Observe that debris is being captured by the negative air machine and not released into the home

- Using only a shop vacuum at the register openings, which does not clean the full length of branch runs

- Blowing debris through the system without capture, contaminating previously clean sections

- Skipping the return side or the air handler components, leaving major contamination sources untreated

- Using chemical encapsulants to cover contamination instead of physically removing it

Sanitizing or antimicrobial treatment should only be applied when mold growth has been confirmed (not as a routine step). Use only EPA-registered antimicrobial products that are specifically labeled for use in HVAC systems, applied per NADCA standards. Before sanitizing, the source of moisture that caused the mold must be identified and corrected; sanitizing alone will not prevent recurrence. Sanitizing is not a substitute for physical cleaning and must be applied only after thorough source removal cleaning is complete.

1. Confirm mold was positively identified (visual confirmation or lab testing) before any sanitizing treatment is applied

2. Verify the product used is EPA-registered and labeled for HVAC system use (request the product data sheet)

3. Confirm the moisture source that caused the mold has been identified and corrected before treatment

4. Verify sanitizing was applied after physical cleaning, not as a substitute for cleaning

5. Check that the product was applied per the manufacturer's instructions for coverage rate and dwell time

- Applying sanitizer routinely when no mold is present (unnecessary chemical exposure and expense)

- Using non-EPA-registered products or products not labeled for HVAC use, which may be toxic

- Sanitizing without fixing the moisture source, leading to mold recurrence within months

- Applying sanitizer without first performing physical cleaning, which is ineffective against established mold

Install a new air filter immediately after duct cleaning is complete (never reuse the existing filter). Select a filter rated MERV 8 minimum for general dust control, or MERV 13 for enhanced allergen and particulate control (recommended for allergy sufferers). Verify the filter size matches the filter slot exactly with no gaps around the edges that allow air bypass. Confirm the filter is installed with the airflow direction arrow pointing toward the blower. Higher MERV ratings (14+) may restrict airflow in older systems; verify the HVAC system can handle the pressure drop.

1. Verify a new filter is installed (not the old filter cleaned and reinstalled)

2. Confirm the MERV rating meets the homeowner's needs: MERV 8 minimum, MERV 13 for allergen control

3. Check the filter size by measuring the slot; the filter should fit snugly with no visible gaps around the edges

4. Verify the airflow direction arrow on the filter frame points toward the blower (toward the air handler)

5. After running the system for 1 hour, check the filter for proper seating and no bypass around the edges

- Filter size slightly wrong, leaving gaps that allow unfiltered air to bypass directly into the system

- Filter installed backwards (against the airflow), reducing effectiveness and increasing resistance

- Choosing a MERV rating too high for the system, restricting airflow and causing the coil to freeze

- Not replacing the filter after cleaning, immediately recontaminating the freshly cleaned ducts

Perform a post-cleaning camera inspection at the same access points used for the pre-cleaning assessment. Compare before and after images to verify visibly clean surfaces throughout the duct system. Test system airflow at representative registers using an anemometer or flow hood to confirm airflow has not been restricted (should maintain or improve from pre-cleaning levels). Verify all access doors are properly sealed, all registers are reinstalled, and no damage was done to ductwork, insulation, or flex duct connections during cleaning.

1. Review post-cleaning camera footage and compare with pre-cleaning images to verify visible improvement

2. Measure airflow at 3-5 representative supply registers; flow should be equal to or better than pre-cleaning

3. Inspect all access doors for airtight seals with no visible gaps or loose screws

4. Verify all supply and return registers are reinstalled, clean, and fully open

5. Check all flex duct connections and duct joints for damage (disconnections, torn insulation, crushed sections)

- No post-cleaning inspection performed, making it impossible to verify the work quality

- Reduced airflow after cleaning due to damaged or disconnected flex duct connections

- Access doors not properly sealed, creating new air leaks that reduce system efficiency

- Duct insulation torn or compressed during cleaning, reducing thermal performance