Gas density

What it's for

Breathing-gas density at depth. High density raises work of breathing, so technical divers cap it.

Formulas

$$\rho =P\sum _i{F}_i{\rho }_i$$

• $\rho$: gas density at depth, g/L.
• $P$: absolute pressure at depth, ata.
• $F_i$: fraction of component $i$ (O₂, N₂, He).
• ${\rho }_i$: density of component $i$ at 0 °C and 1 atm: O₂ 1.42897, N₂ 1.2506, He 0.17846 g/L.

Limits used by the library:

• Recommended maximum: 5.2 g/L.
• Hard maximum: 6.3 g/L.

depthForDensity inverts the formula for a density target.

Assumptions and limits

• Ideal gas: density is proportional to pressure. There is no compressibility correction.
• Component densities are taken at 0 °C, not at a breathing temperature.
• The limits are exported as RECOMMENDED_MAX_DENSITY and HARD_MAX_DENSITY. The library does not enforce them.

Sources

• Component densities: CRC Handbook of Chemistry and Physics.
• 5.2 and 6.3 g/L limits: Anthony & Mitchell, Rebreathers and Scientific Diving (2016).

Examples

import { AIR } from 'dive-math/gas'
import { densityAtDepth, depthForDensity } from 'dive-math/density'
densityAtDepth(AIR, 30) // => 5.15
depthForDensity(AIR, 5.2) // => 30.38

API

See the density API reference.