ppbv
part per billion by volume (moisture)
One part per billion by volume of moisture is 0.621945 × 10⁻⁹ kg/kg on the same dilute linearisation as ppmv. Ultra-high-purity gases for semiconductor fabrication are specified in ppbv, where single-digit values are routine and the linearisation is essentially exact.
Watch out: At these levels the reading is dominated by outgassing from the delivery system. A ppbv specification refers to the gas at the cylinder, and the moisture at the tool depends on the tubing, the fittings and how long the line has been purged.
| 1 ppbv | 6.2194500e-07 g/kg |
Solvers that use humidity ratio