| Term | Definition/Description |
| TLV | The Threshold Limit Value is a recommended occupational exposure guideline published by the American Conference of Governmental Industrial Hygienists. TLV’s are expressed as parts of vapor or gas per million parts of air by volume (ppm) or as approximate milligrams of particulate per cubic meter or air (mg/M3). The TLV is the average concentration of a chemical that most people can be exposed to for a working lifetime with no ill effects. The TLV is an advisory guideline. If applicable, a ceiling concentration (C), which should not be exceeded, or a skin absorption notation (S) will be indicated with the TLV. |
| PEL | The permissible exposure limit is a legal standard issued by OSHA. Unless specified, the PEL is a time weighted average (TWA). |
| TWA | Most exposure standards are based on time weighted averages. The TWA is the average exposure over an eight (8) hour work day. Some substances have Ceiling (C) limits. Ceiling limits are concentrations that should never be exceeded. The SDS will list the occupational health standard(s) for the hazardous chemical or each component of a mixture. |
