A settling chamber is used for the removal of discrete particulate matter from air with following conditions. Horizontal velocity of air $=0.2 \mathrm{~m} / \mathrm{s}$; Temperature of air stream $=77^{\circ} \mathrm{C}$; Specific gravity of particle to be removed $=2.65$; Chamber length $=12 \mathrm{~m}$; Chamber height $=2 \mathrm{~m}$; Viscosity of air at $77^{\circ} \mathrm{C}=2.1 \times 10^{-5} \mathrm{~kg} / \mathrm{m} . \mathrm{s}$; Acceleration due to gravity $(\mathrm{g})=9.81 \mathrm{~m} / \mathrm{s}^{2}$; Density of air at $77^{\circ} \mathrm{C}=1.0 \mathrm{~kg} / \mathrm{m}^{3}$; Assume the density of water as $1000 \mathrm{~kg} / \mathrm{m}^{3}$ and Laminar condition exists in the chamber.
The minimum size of particle that will be removed with $100 \%$ efficiency in the settling chamber (in $\mu \mathrm{m}$ ) is $\_\_\_\_\_\_\_\_\_\_\_\_\_$ (round off to one decimal place).
