A notation, sometimes used with PEL or TLV exposure date; indicates that the stated substance may be absorbed by the skin, mucous membranes, and eyes-either by airborned or by direct contact-and that this additional exposure must be considered part of the total exposure to avoid exceeding the PEL or TLV for that substance.

Importance: Even if workplace concentrations of a chemical do not exceed the TLV or PEL, the risk to health may be severe becuase breating and skin contact are combined. Skin protection is advised.