Design criteria are given for cotton processing machinery local exhaust ventilation systems for maintaining dust concentration in the work area in yarn making below 0.5 milligrams per cubic meter of air, with data given for assessment of the ability of dust capture devices to maintain concentrations of 0.2 to 0.1 milligrams by increasing quantity of air handled. Cotton dust filtration is analyzed, with characteristics of cotton dust and of air cleaners. Lint and dust control systems, and capture devices, are described for carding, combing, drawing, picking, and opening operations and production units. Cotton dust is judged to be controllable at the recommendations that research be continued for development of equipment which will effectively control cotton dust particles of 15 microns or less. Control equipment discussed include: wet separators, settling chambers, cyclones, mechanical collectors, electrical precipitators, rotary drum filters, continuous automatic lint and dust filter systems, primary separators, secondary separators, tertiary separators, waste separators, elutriators, and samplers.