Even with good filters in place, many HVAC systems contain hidden components that trap and release dust—especially older ductwork, internally insulated plenums, or open wall cavities used as return chases. These hidden spaces can harbor mold, microbial growth, and decades of accumulated debris.

Key areas to inspect or upgrade:

• Internally insulated plenums and registers: These materials are often impossible to clean thoroughly. Replace them with externally insulated metal components.
• Open wall cavity returns: These should be replaced with properly ducted ceiling or wall-mounted return ductsto prevent drawing in wall dust and debris.
• Flexible ductwork: If it’s contaminated or degraded, it should be removed and replaced—not cleaned.

Have these components inspected by a licensed HVAC professional familiar with environmental sensitivity and remediation standards. Proper sealing, insulation, and upgrades can dramatically reduce recontamination from your system.