Evaluation of air cleaner efficiencies for particles greaser than 1 µm can be quite demanding, depending on the accuracy required. Such particles have sufficient mass to require consideration of sedimentation and inertial losses. The challenge aerosol is usually generated by dispersion of a dry powder or by liquid spray. In-duct particle measurements are preferred to extractive instruments because of particle loss in sampling tubes. Large particles are also sensitive to nonisokinetic sampling effects.

Units: SI