CO2 Pocket at the Sleep Station (2D)

Sleep Station Controls

Breathing rate 15 br/min

Ventilation fan 0%

Vent duct distance 0.60 m

Time acceleration 6×

Head-Level Readouts

Safe

CO2 near face

400 ppm

Sleep elapsed

0.0 min

Net removal rate

0.15 /min

Equilibrium level

9300 ppm

Drag the diagram to pan, scroll or pinch to zoom in on the CO2 pocket around the head.

How it works

On the ground, warm exhaled CO2 rises away from a sleeper's face — a buoyancy-driven convection current. In orbital free-fall there is no "up", so that current does not exist: molecular diffusion is far too slow to clear the roughly 300 mL of CO2 exhaled every minute, and it collects in a stagnant pocket right around the head. Real ISS crews have reported waking with headaches when a sleep-station fan failed — flight rules now mandate airflow at every crew quarter.

This 2D redraw uses the exact same mass-balance ODE as the 3D version — same constants, same equilibrium formula, verified numerically to converge to the analytic steady state below to within floating-point error — and renders it as a flat, pannable/zoomable cross-section instead of an orbit-camera scene:

dC/dt = P/V − (k_diff + k_fan)·(C − C_ambient)
P  = CO2 production rate (∝ breathing rate)
V  = local pocket volume
k_diff = weak baseline mixing (diffusion + cabin leakage)
k_fan  = fan_power × (ref_distance / vent_distance)²

Breathing rate — scales CO2 production P; faster breathing (restless sleep, exertion before bed) raises the source term.
Ventilation fan — the only real removal mechanism in microgravity; 0% reproduces the historical "fan-off headache" reports.
Vent duct distance — airflow strength falls off with the square of distance from the duct to the sleeper's head.
Equilibrium level — the steady-state concentration C = C_ambient + P·V⁻¹ / (k_diff + k_fan) the pocket is heading toward; watch it fall as you turn the fan up.

Risk bands loosely follow NIOSH/OSHA CO2 exposure guidance: under 1,000 ppm is unremarkable indoor air, 1,000–5,000 ppm brings drowsiness and headache risk over a sleep shift, and above 5,000 ppm is treated as an occupational exposure limit exceedance.

Vent duct CO2 concentration

drag to pan · scroll to zoom