STANDARD_AIR

Dry air at 20 °C and one atmosphere, at 50% relative humidity.

Explained in Chemistry.

const STANDARD_AIR: AmbientState

import { STANDARD_AIR } from '@driftengine/chemistry';

In depth

Argon is lumped into nitrogen, per the species table's own note: it is 0.93% of air and chemically inert, so all it contributes is heat capacity and dilution. What that costs is measurable and small — the mean molar mass comes out at 28.86 g/mol against air's real 28.96, which is 0.4% — and what it buys is not carrying a sixteenth element for a gas that never reacts.

The mass fractions are chosen so the volume fraction of oxygen comes back at 20.95%, because that is the number every extinction criterion in §12 is written against.