Avenida Balboa runs along the bay and the Cinta Costera, and many of its residential towers, hotels and offices face the sea. There are also glass façades.
The sea breeze brings salty air and humidity, which join the moisture of the ambient air and the water the unit itself condenses. Glass raises the thermal load and the system runs more hours, so more air, with its dust, passes through the same ducts. That is why the review does not stop inside the duct: it also looks at what stays in view in grilles, frames and air intakes. The effect of salt on equipment is explained in why air conditioning corrodes near the sea. The area is about 5 km by road from the Climatiza office, in an approximate calculation.
Data point: At the Tocumen station the mean relative humidity drops to 64.9% in March, the least humid month, and rises to 82.4% in October (ETESA, 1977 to 2010, in Spanish). The EPA recommends keeping indoor air below 60%.