This document discusses flammable gases and their explosive limits when mixed with oxygen in air. It notes that air contains about 21% oxygen and defines the lower and upper explosive limits as the concentration ranges of a flammable gas or vapor mixed with air below and above which it is not explosive, providing methane, propane and hydrogen as examples with their percentage ranges.

1. The gases that we are concerned with are flammable
with combined with oxygen in air.
There is about 21% of oxygen i air.
Th i b t f in i
Lower explosive limit. The Concentration of flammable
gas or vapor in air below which the gas is not
explosive.
Upper explosive limit. The concentration of flammable
gas or vapor in air above which the gas is not
explosive.
Range
Methane – 5% to 15%
Propane -1.5% t 9%
P 1 5% to