RKI Instruments GX-8000(PT0-098) - Manual (Page 51)

10 Definition of Terms 9-2. List of accessories
- 51 - GX-8000
10
Definition of Terms
vol% Gas concentration indicated in the unit of one-hundredth of the volume
ppm Gas concentration indicated in the unit of one-millionth of the volume
%LEL An abbreviation for "Lower Explosion Limit."
LEL refers to the lowest concentration of a combustible gas in air capable of
causing explosion when ignited.
TWA An abbreviation for "Threshold Limit Value Time Weighted Average Limit." TWA
refers to a concentration limit of toxic substances as a time weighted average to
which repetitious exposure of almost all the workers in 8-hour work shift or a
40-hour work week does not have harmful effects on their health.
STEL An abbreviation for "Threshold Limit Value Short Term Exposure Limit." STEL
refers to a concentration limit of toxic substances to which everyday exposure of
workers for 15 continuous minutes lower than TWA does not have harmful
effects on their health.