Not every home has ducts. Many apartments use wall units with no duct network, and in those cases there is no ductwork to clean. Where there is a central system or a network hidden above the ceiling, the inside of the ducts cannot be seen from the room, and inspection is the way to find out.
The most cited public reference for homes is the EPA guide. It says when cleaning makes sense (visible mold, pests, excess dust or debris, or particles coming out of the grilles) and clarifies that duct cleaning has never been shown to prevent health problems. In a climate as humid as Panama’s, the starting point is to look at the system and decide based on what is seen.
Data point: In minisplit-type units in homes in Japan, high-pressure washing reduced the internal fungal load by more than 99%, and a year later it had returned to the previous level (Shiraishi et al., 2023 and 2026). It is a different kind of equipment and is cited as context.