PPB Definition - Parts Per Billion

PPB stands for parts per billion. One part per billion is one part of solute per one billion parts solvent. PPB is a commonly used unit of concentration for very small values. The parts per notation is not part of the SI system of units. The notation describes dimensionless quantities. The ppb notation is most often seen in physics and engineering. In chemistry, the use of SI-compliant units is encouraged. Source Schwartz and Warneck (1995). Units for Use in Atmospheric Chemistry. Pure Appl. Chem. 67: 1377–1406.