The character of cotton dust in an experimental card room and in a remote room used for exposing human volunteers to cotton dust was affected by the cleaning level at the gin, the quantity of air used in the card dust collection system and the card production rate. Increased levels of gin cleaning and increased quantitates of air in the card dust collection system generally increased the respirable fraction and decreased the mass median diameter. Increased card production rates reduced the respirable fraction and increased the mass median diameter.

About 90-95 percent of all dust particles were less than 1.98 µm but their mass constituted no more than 50 percent of the total. Essentially, all particles were less than 11.9 µm but those in excess of 11.9µm constituted as much as 10 percent of the total mass. The mass median diameter of dust in the remote room was about 1µm less than that of card room dust.