TLV — Threshold Limit Value — is a chemical term referring to the amount of a substance, liquid or gas to which one can be exposed before physical effects will begin to occur.
TLV is used with TWA (Time Weighted Average), the maximum allowed concentration in the occupational breathing space of an airborne contaminant, over an eight-hour day. Very important information obtained from MSDS sheets when dealing with solvents used for film cleaning.