Can you use PVC and cpvc pipe in a open plenum ceiling?

Using PVC and CPVC pipe in an open plenum ceiling is generally not recommended due to fire safety concerns. These materials can emit toxic fumes when exposed to high temperatures or flames, which poses a risk in spaces designed for air circulation and potentially housing electrical components. It's essential to consult local building codes and regulations, as they may specify acceptable materials for plenum spaces. Always consider using materials specifically rated for such environments, like metal ductwork, to ensure safety and compliance.