My desk at work is often covered by large black particles. They are messy and I am concerned that I may be exposed to something that is harmful to my health. USA The problem you describe is common in buildings with mechanical ventilation systems. The particles though black and unpleasant looking are too large to pose any health risk to you or others.
Neoprene is pigmented with carbon black which is produced from the burning of oil.
The size range for carbon black particles is in the range of 0.1-0.5 micrometers in diameter. Because of the very small size of carbon black particles they can pose a significantly higher health risk than the particles which are landing on your desk. Fortunately the carbon black particles are incorporated in to the matrix of neoprene. Because neoprene is a polymer it begins to crack when it is exposed to atmospheric ozone even at the low levels that are naturally present in outside air. Higher ozone concentrations in urban areas accelerate the cracking of the neoprene coating on duct liner materials.