What should be avoided in areas using a ceiling space for air return?

In areas using a ceiling space for air return, it is essential to avoid combustibles because these materials can pose a significant fire hazard. The ceiling space is often not designed for storage or to accommodate flammable materials. If combustibles are present, they can ignite from sparks or excessive heat and lead to potentially catastrophic consequences. Ceiling spaces may be involved in air return paths, and any presence of combustibles can obstruct airflow and pose a danger to the entire HVAC system and surrounding areas.

While multiple ducts, heavy insulation, and flat surfaces can also complicate air return systems, they do not inherently present the same immediate fire risk that combustibles do. Multiple ducts could lead to a more complex air return design, heavy insulation may affect thermal performance but isn’t a fire hazard, and flat surfaces can trap dirt and debris but do not directly pose a fire threat. Therefore, avoiding combustibles is critical for maintaining safety in spaces where air is returned through ceilings.