Safety: Making Sense of MSDS Terminology, Part 8

Dec. 23, 2013
Make sure you clearly understand these four MSDS and product label terms.

Product labels and an MSDS include terminology that you might be unfamiliar with. Here are four terms you should clearly understand.

Permissible Exposure Limit (PEL). This is a daily exposure limit that OSHA considers to be safe. You can’t aggregate or average exposure times; if you go over the PEL on any given day, that’s a reportable event.

Threshold Limit Value (TLV). This is similar to the PEL. But instead of being set by OSHA, it’s set by the American Conference of Government Industrial Hygienists (ACGIH). If these numbers disagree, go with the lower number. The OSHA number, if higher, will apply as a legal reporting requirement.

Reactivity. The higher the reactivity, the more likely a substance is to react with another substance. Hydrogen, chlorine, fluorine, and oxygen have high reactivity. Nitrogen is an inert gas (no reactivity). Low reactivity doesn’t mean something is safe. Many people have died after improperly entering a vessel that’s been purged with nitrogen.

Solubility. How rapidly or completely a substance will dissolve when placed in a solvent (typically, water).

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