1.1 ,This practice covers the determination of the particle concentration, by number, and the size distribution of airborne particles in dust-controlled areas and clean rooms, for particles in the size range of approximately 0.01 to 5.0 μ,m. Particle concentrations not exceeding 3.5 ,×, ,10⁶ particles/m ³ (100 ,000/ft³) are covered for all particles equal to and larger than the minimum size measured.