Which cleaning method is not effective in ensuring contaminants are removed from an HVAC system?

The method of dry cleaning with rags is less effective in ensuring that contaminants are entirely removed from an HVAC system because it typically relies on the physical action of wiping surfaces without the use of moisture or specialized cleaning agents. This can leave behind particles, dust, and microbial agents rather than eliminating them.

In contrast, mechanical agitation effectively loosens contaminants, allowing for their removal. HEPA vacuuming is crucial as it captures tiny particles and allergens that may not be visible, ensuring thorough cleaning by using high-efficiency particulate air filters. Wet wiping, on the other hand, dampens surfaces, which not only helps lift contaminants but also reduces the risk of them becoming airborne during the cleaning process. Thus, while all these other methods contribute to an effective cleaning strategy, dry cleaning with rags may not achieve comprehensive removal of contaminants in an HVAC system.