Glossary of Terms
| Term |
Definition |
| dB |
Decibel - a unit used to measure the relative power of sound. A 3db increase in sound output power represents a doubling of the perceptible volume. |
| LCD |
Liquid Crystal Display - an electronic visual display that uses the light modulating properties of liquid crystals. |
| LEL / LFL |
Lower Explosive Limit / Lower Flammable Limit - the minimum concentration at which a gas will explode. A common unit of measurement is a percent of the LEL. |
| PID |
PhotoIonization Detector - an instrument that utilises ultra-violet light energy to ionize and detect the presence of an unknown gas or vapor. |
| PPM |
Part Per Million - a common unit of measurement for toxic gases. This term literally means one part out of one million possible parts. |
| STEL |
Short Term Exposure Limit - the average amount of gas (in PPM) a worker can be exposed to in a 15 minute period with no long term health effects. For example, this may occur 4 times a shift with one hour between 15 minute exposures. |
| TWA |
Time Weighted Average - the average amount of gas (in PPM) a worker can be exposed to over a certain time period. This time is defined as 8 hours to represent a normal work day. |
| UEL/UFL |
Upper Explosive Limit/Upper Flammable Limit - the maximum concentration at which a gas will explode. |
| VAC |
Volts Alternating Current - an electric current that reverses direction at regular intervals. |
| VDC |
Volts Direct Current - an electric current of constant direction. |
| VOC |
Volatile Organic Compound - any compound containing carbon, except methane, that can be easily vaporized. |
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