Environmental Health and Safety

MSDS Glossary

UEL, or UFL
Upper explosive limit or upper flammable limit of a vapor or gas; the highest concentration (highest percentage of the substance in air) that will produce a flash of fire when an ignition source (heat, arc, or flame) is present. At higher concentrations, the mixture is too "rich" to burn. See also LEL.
ug
Microgram, one millionth of a gram.
Unstable
Tending toward decomposition or other unwanted chemical change during normal handling or storage.
Unstable Reactive
A chemical that, in the pure state, or as produced or transported, will vigorously polymerize, decompose, condense, or become self-reactive under conditions of shock, pressure, or temperature.

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