Dusts, fumes and smoke Other workplace processes can generate tiny solid particles which are light enough to float in the air, and these are referred to as dusts, fumes and smoke. Dusts are solid particles often generated by some mechanical or abrasive activity. They are usually heavy enough to settle slowly to the ground. Fumes are very tiny solid particles which can remain airborne that are formed when a heated metal has evaporated in the air and then condensed back to a solid form. This occurs in welding operations.
Smoke is carbon or soot from burning.
Smoke particles can settle or remain airborne depending on their size. Chemicals which pass through the skin are nearly always in liquid form. Solid chemicals and gases or vapours do not generally pass through the skin unless they are first dissolved in moisture on the skin's surface. The skin is the second most common route by which occupational chemicals enter the body. It consists essentially of two layers, a thin, outermost layer called the epidermis and a much thicker underlayer called the dermis.