There are black particles deposited on supply air diffusers – what is it and is it harmful?
These black particles are typically from normal airborne particulates (e.g. carbon black and dust) found in room air, which, when entrained into the discharge air from the diffusers, impinges upon the diffuser. Also keep in mind that if you can see the particles, they are too large to be respired down into the lungs – rather, they become lodged in the nasal passages of the upper respiratory system.
