They're released when moldy hay, silage, or grain is disturbed. Mists are suspended liquid droplets and are usually found ear mixing, spraying, and cleaning operations. Fumes are solid particles of evaporated metal. They're microscopic as well and are formed during activities such as welding. The second category of hazards is gases and vapors.
Vapors evaporate from liquids, such as pesticides, paints, adhesives, and lacquer thinner.
Gases are chemicals that are gaseous at room temperature. The third category of hazards is oxygen-deficient atmospheres. The reduction in oxygen may occur deliberately, such as with CA storages, or is displaced by other gases as in manure storage's and conventional silos. For example, maybe you could use different management practices when harvesting and storing crops to reduce dust and mold. Perhaps you need better ventilation in your barn.