Hi, thanks for your answers. I would rather not open my (AppleCare covered) machine -if I can- to clean the fan, although it's very tempting to do so. iFixers by nature, right? Either way, I will try to use the canned air trick as suggested.
At the same time, I decided to try (ordered) the "COREFILTER - Air Filter Base for Apple Mac Pro" to provide the base of the machine a dust filter. Will provide feedback regarding the fitting, use, dust capture, cleaning, airflow, etc, if desired. It's not a sales pitch or promo, just feedback on an attempt to solve the dust-problem.