ODM2 Units Type Controlled Vocabulary ODM2 Working Group A vocabulary for describing the type of the Unit or the more general quantity that the Unit represents. 0 Dimensionless Ratio 0 0 0 unitless 0 new for ODM2 Concentration volume per volume 0 0 L3L-3 The volume of one substance per unit volume of another substance. This is used for volume percents or the ppm of a gas mixture.