Adhesion and Aerodynamic Resuspension of Fibrous Particles

Under a simplifying assumption of uncharged particles, the adhesion theory was used in conjunction with the boundary layer theory to derive an expression for the lower limit of velocity for the resuspension of fibrous particles from flat surfaces. The theory, albeit approximate, suggests that mineral fibers with diameters less than 9 μm diameter will not be resuspended by bulk air velocities less than 10 m/s. Since electrostatic forces, fiber orientation or high humidity will require a higher aerodynamic force to lift the fibers off a surface, this theoretical limit is conservative for environmental exposure considerations. The theoretical calculations were experimentally confirmed by observing the behavior of settled single fibers in turbulent air flow. The results of the theoretical analysis and the subsequent experimental confirmation suggests that the concerns about the aerodynamic resuspension of mineral fibers within a biologically significant size range are overstated.