Glossary

Glossary for RAE Systems Applications and Technical Notes

Note: Definitions in this glossary are elementary and only intended to aid understanding by persons without a chemistry or electronics background. Words contained in a definition that are in bold text are defined elsewhere in the glossary.

 

Benzene - Benzene is a chemical that is often used in manufacturing. In its most common form, benzene is a liquid that is clear, slightly sweet smelling, and highly combustible. Benzene is frequently used in manufacturing rubber, paint, plastics, resins, drugs, pesticides, synthetics, and other products. It is also present in gasoline and tobacco

 

Electromagnetic - magnetism produced by an electric current

 

Hydrocarbon – an organic chemical compound containing only hydrogen and carbon atoms

 

IBE – Isobutylene, a common calibration gas for PIDs.

 

Ion - An atom or a group of atoms that has acquired a net electric charge by gaining or losing one or more electrons; from the Greek word ion, meaning to go

 

Ionization – The formation of or separation into ions by heat, electrical discharge, radiation, or chemical reaction.

 

IE or IP – Ionization Energy or Ionization Potential; More correctly termed ionization energy and commonly given in units of electron-volts (eV). This is the lowest photon energy capable of ejecting an electron from a target molecule

 

Ionization Potential – See IE.

 

Isobutylene - Isobutylene - C4H8 - in its pure form is used in organic synthesis and in the production of high octane aviation gasoline. Its main use is in the production of Butyl rubber where it comprises 98% of the raw material used.

 

LEL or LFL - Lower Explosive Limit or Lower Flammability Limit; the lowest vapor concentration that will sustain a flame when ignited in air.

 

MOS – Metal Oxide Semiconductor; A type of semiconductor device commonly used in most electronic circuits. Some sensors employ this technology for gas detection.

 

NIOSH – National Institute for Occupational Safety and Health; the U.S. government agency that recommends non-enforceable exposure limits (RELs).

 

Octane – a liquid hydrocarbon found in petroleum. From Late 19th century. Coined from octo- + -ane; from the number of carbon atoms in the hydrocarbon.

 

Organic – Chemistry: Of or designating carbon compounds with more than one carbon atom and typically containing Hydrogen atoms; from Greek organon, literally, tool, instrument partly from Old French organe, from Latin organum; akin to Greek ergon work

 

Photon – A quantum of visible light or other form of electromagnetic radiation. Late 19th century. Via French from Greek phōt- , stem of phōs “light.

 

PID – Photo Ionization Detector; A device that excites the electrons in an atom by striking the atoms with photons, causing the atoms to ionize, the charge of the ionized atoms is then measured by an electronic circuit.

 

ppb – Parts Per Billion. The ratio, expressed in billions, of two substances, e.g., if a substance has 5 parts of A and 1 Billion parts of B then it is 5ppb (0.0000005%).

 

ppm – Parts Per Million. The ratio, expressed in millions, of two substances, e.g., if a substance has 10 parts of A in 1 million parts of B then it is 10ppm (.000001%).

 

Quantum – physics: the smallest unit used to measure a physical property. For example, the quantum of electromagnetic radiation is the photon.

 

REL – Recommended Exposure Limit as suggested by NIOSH

Resistance – the property of a resistor that inhibits the flow of electric current in an electronic circuit

 

Resistor – an electronic component that resists the flow of electric current in an electronic circuit.

 

Semiconductor – a partially conductive solid: a solid such as silicon or germanium that has electrical conductivity between that of a conductor and an insulator

 

VOC – Volatile Organic Compound; In general use this acronym refers to all organic compounds that have significant vapor pressure.

 

Volatile – Chemistry-
a. Evaporating readily at normal temperatures and pressures.
b. That can be readily vaporized.
French, from Old French, from Latin volatilis, flying, from volatus, past participle of volare, to fly

 

STEL – Short Term Exposure Limits; the maximum allowable exposure concentration over a 15-minute period for at most 3 times per 8-hour day separated by at least one hour exposure below the TWA

 

TWA – Time Weighted Average; A cumulative exposure, generally over an 8-hour period. TWA is calculated as the average concentration times the fraction of the (8-hr) time period elapsed.

 

Vapor – physics- the gaseous state of a liquid or solid at a temperature below its boiling point

 

Vapor Pressure – the pressure exerted by a vapor, particularly a vapor in contact with its liquid form

 

Wheatstone bridge – An electronic device used to determine an unknown resistance by adjusting a known resistance so that the known value and unknown value are balanced and the measured current is zero. In principal, the Wheatstone bridge works much like the doctors scale where known weights are used to null the scale against the unknown weight of the patient.