Latent period
The time that elapses between exposure and the first manifestation of damage.

LC50
Lethal concentration that will kill 50 percent of the test animals within a specified time. See LD50.

LD50
The dose required to produce the death in 50 percent of the exposed species within a specified time.

Liter (L)
A measure of capacity - one quart equals 0.9L.

Lower explosive limit (LEL)
The lower limit of flammability of a gas or vapor at ordinary ambient temperatures expressed in percent of the gas or vapor in air by volume. This limit is assumed constant for temperatures up to 120oC (250oF). Above this, it should be decreased by a factor of 0.7 because explosibility increases with higher temperatures.