Which methods are used to verify duct cleanliness?

• A. Gas chromatography
• B. Pressure testing
• C. Visual inspection
• D. White glove, swab, dust collection

Answer: (D)

After duct cleaning, you verify cleanliness by directly assessing residual dust and debris on surfaces and in the ducts. A white glove test gives a quick, hands-on read on surface cleanliness by checking for visible dust transfer when a clean glove is wiped over surfaces. Swab sampling collects surface residues for laboratory analysis, yielding a concrete measure of how much contamination remains. Dust collection provides a quantitative measure of the total particulate load left behind, helping to confirm the overall cleanliness level.

Gas chromatography is for analyzing specific chemicals and isn’t a routine method for confirming general duct cleanliness. Pressure testing assesses airflow or leaks, not cleanliness. Visual inspection can catch obvious dirt but is subjective and may miss fine residues, so combining it with swab and dust analyses offers a more reliable verification.