Sleeper (OccupantAtmospherics)

The Sleeper is the device a player lies in to safely log out. This page documents its atmosphere subsystem: where the occupant's breathed air actually comes from, the device's safe-atmosphere check, its passive heater, and the conditions under which it suspends metabolism. The sleep/stun mechanic itself (how the occupant is put and held unconscious) lives in StunStateMachine.md; the breathing/oxygenation math lives in BreathingAndOxygenation.md.

Class hierarchy: Sleeper : OccupantAtmospherics : SpawnPointAtmospherics : DeviceInputOutput. CryoTube is a sibling (CryoTube : OccupantAtmospherics, ILifeSuspender, ICryogenicRegenerator) that adds a separate coolant loop; see Open Questions for what was not traced here.

The occupant breathes the piped-in internal atmosphere, not the room

This is the central and most misread fact. A human in a Sleeper does NOT breathe the room the sleeper sits in. They breathe the device's internal atmosphere, which is the gas on the connected pipe network.

The mechanism is Thing.SetWorldAtmosphere() (line 281183):

public void SetWorldAtmosphere()
{
    Slot parentSlot = ParentSlot;
    if (parentSlot != null)
    {
        if (parentSlot.UseInternalAtmosphere)
        {
            WorldAtmosphere = parentSlot.Parent.InternalAtmosphere;
            return;
        }
        if ((bool)parentSlot.Parent.AsDynamicThing)
        {
            WorldAtmosphere = parentSlot.Parent.AsDynamicThing.WorldAtmosphere;
            return;
        }
        Thing thing = parentSlot.Parent?.RootParent ?? this;
        WorldAtmosphere = base.GridController.AtmosphericsController.SampleGlobalAtmosphere(thing.WorldGrid);
        return;
    }
    WorldAtmosphere = base.GridController.AtmosphericsController.SampleGlobalAtmosphere(base.WorldGrid);
    ...
}

When the occupant sits in a slot whose UseInternalAtmosphere flag is set (the sleeper's bed slot), the occupant's WorldAtmosphere is bound to parentSlot.Parent.InternalAtmosphere, i.e. the sleeper's internal atmosphere. A human with no sealed-suit internals reads that as its breathing atmosphere (Human.BreathingAtmosphere at line 340241 returns base.BreathingAtmosphere -> Entity.BreathingAtmosphere at 283661 -> base.WorldAtmosphere). See BreathingAndOxygenation.md "Which atmosphere is breathed".

The device confirms this in its own UI: the info-panel tooltip (line 399496-399497) prints the GameStrings.BreathingAtmosphere label (localized "Occupant Atmosphere") and renders the gas contents of base.InternalAtmosphere:

stringBuilder.AppendLine(GameStrings.BreathingAtmosphere.AsColor("white"));
AtmosphericsManager.MakeGasTooltip(base.InternalAtmosphere, stringBuilder, indent: true);

Consequence: to keep a sleeping occupant healthy you pipe a breathable atmosphere into the sleeper's gas input. The room around the sleeper is irrelevant while the door is closed.

Door open exception: SpawnPointAtmospherics.OnAtmosphericTick (line 401387) mixes the internal atmosphere with GetWorldAtmosphere() (the room) instead of the pipe when IsOpen, and an open sleeper drops to the Inactive mode and shows the red SleeperDoorIsOpen string (399513-399520). A closed, powered sleeper uses the pipe.

Internal atmosphere volume and pipe wiring

Sleeper.InitInternalAtmosphere() (line 399681) creates an 800 litre internal atmosphere:

public override void InitInternalAtmosphere()
{
    if (base.InternalAtmosphere == null)
    {
        base.InternalAtmosphere = new Atmosphere(this, new VolumeLitres(800.0), 0L);
    }
}

The base SpawnPointAtmospherics.InitInternalAtmosphere() (line 401100) defaults to 10 litres; the Sleeper overrides to 800.

Each atmospheric tick (SpawnPointAtmospherics.OnAtmosphericTick, line 401381) the internal atmosphere is mixed toward the input network's atmosphere (gas), and liquids are drained from the pipe:

if (base.InternalAtmosphere == null || InputNetwork?.Atmosphere == null)
{
    return;
}
AtmosphereHelper.Mix(base.InternalAtmosphere, IsOpen ? GetWorldAtmosphere() : InputNetwork.Atmosphere, AtmosphereHelper.MatterState.Gas);
if (!IsOpen)
{
    AtmosphereHelper.DrainLiquids(base.InternalAtmosphere, InputNetwork.Atmosphere, Chemistry.PipeVolume);
}

Sleeper.AssessError() (line 399702) sets OutputNetwork = InputNetwork, so the device sits on a single connected pipe network rather than pumping from a distinct input to a distinct output. A missing pipe yields the red CryoNoAtmosphericInput string (399521-399527).

Safe-atmosphere check (IsUnsafeAtmosphere)

OccupantAtmospherics holds the device limits (lines 399447-399449):

private TemperatureKelvin _minimumTemperature = new TemperatureKelvin(263.15);  // -10 C
private PressurekPa _minimumPressure = new PressurekPa(30.0);                   // 30 kPa

IsUnsafeAtmosphere (lines 399457-399478) evaluates the device's own internal atmosphere:

public bool IsUnsafeAtmosphere
{
    get
    {
        if (base.InternalAtmosphere == null) return true;
        if (base.InternalAtmosphere.PressureGassesAndLiquids < _minimumPressure) return true;   // < 30 kPa
        if (base.InternalAtmosphere.Temperature > Chemistry.Temperature.FiftyDegrees) return true; // > 50 C (323.15 K)
        // ... (intervening lines)
        if (base.InternalAtmosphere.Temperature < _minimumTemperature) return true;             // < -10 C (263.15 K)
        return false;
    }
}

So the device considers its internal (piped) atmosphere unsafe if pressure is below 30 kPa or temperature is outside the -10 C to +50 C band. An unsafe atmosphere yields the red CryoAtmosphereIsUnsafe string (399529-399535) and flips the device to the Error mode (OnServerTick, line 399596).

Important gap: IsUnsafeAtmosphere does NOT check oxygen content. A nitrogen-only atmosphere at 50 kPa and 20 C passes the device's safe check, but the occupant's lungs still need at least 16 kPa O2 partial pressure (Chemistry.MinimumOxygenPartialPressure) to refill oxygenation. The green device light is necessary but not sufficient for occupant health; the player must ensure O2 themselves. See BreathingAndOxygenation.md.

Passive heater toward 24 C

SpawnPointAtmospherics defines _maxHeatKelvin = 297.15 K (24 C, line 401094). At the end of OnAtmosphericTick (lines 401416-401421) the device adds heat to its internal atmosphere up to that target, but only when the atmosphere is above the Armstrong limit and currently below 24 C:

if (base.InternalAtmosphere != null && base.InternalAtmosphere.IsAboveArmstrong() && base.InternalAtmosphere.GasMixture.Temperature <= _maxHeatKelvin && _maxHeatKelvin - base.InternalAtmosphere.GasMixture.Temperature > TemperatureKelvin.Zero)
{
    MoleEnergy val = IdealGas.Energy(base.InternalAtmosphere.GasMixture.HeatCapacity, _maxHeatKelvin - base.InternalAtmosphere.GasMixture.Temperature);
    base.InternalAtmosphere.GasMixture.AddEnergy(RocketMath.Min(MaxEnergyPull, val));
    _powerUsedDuringTick = RocketMath.Min(MaxEnergyPull, val).ToFloat();
}

MaxEnergyPull = 250 MoleEnergy (line 401084) caps heating per tick. The device warms cold piped gas toward 24 C but does not cool hot gas, so piping in atmosphere hotter than 50 C trips IsUnsafeAtmosphere with no relief.

Operating conditions and metabolic suspension

Sleeper.IsSuspendingLife => Powered (line 399670). The ILifeSuspender contract is what skips the occupant's nutrition, hydration, mood, and hygiene ticks while suspended (see BreathingAndOxygenation.md and StunStateMachine for the life-tick short-circuit). Breathing and organ damage still run, so a suspended occupant can still suffocate, freeze, cook, or be poisoned through the piped atmosphere.

Sleeper.IsOperable (lines 399641-399645) gates the green "metabolic suspension" state on both a valid input and a safe atmosphere:

bool flag = base.IsInputValid && !base.IsUnsafeAtmosphere;

OnServerTick (line 399596) maps the device to one of Standby / Error / Inactive / Occupied / Dead based on power, door state, IsUnsafeAtmosphere, and occupant presence/death.

The stun handling that puts and keeps the occupant asleep (STUN_PER_TICK = 10, STUN_MAX = 100, lines 401086-401088, 401396-401414) is in SpawnPointAtmospherics.OnAtmosphericTick; full detail in StunStateMachine.md.

Practical: optimal atmosphere to pipe into a Sleeper

Hard requirements that must all hold in the piped (internal) atmosphere:

• Total pressure at least 30 kPa (device _minimumPressure). Stay below Chemistry.Limits.PressureMaximumSafe (607.95 kPa).
• Oxygen partial pressure at least 16 kPa (Chemistry.MinimumOxygenPartialPressure) for full breathing efficiency; the device does not enforce this, the lungs do.
• Temperature between -10 C and +50 C (device IsUnsafeAtmosphere, and the human lung damage band is the same -10 C to +50 C). The device heats toward 24 C.
• Methane + Pollutant partial pressure below 0.5 kPa (warning) / 1.0 kPa (lung toxic damage). NitrousOxide below 5 kPa (stun damage).

Robust optimum: standard breathable station air, about 100-101 kPa total, roughly 21 kPa O2 partial pressure with the balance nitrogen, at 20-24 C, free of pollutants. Nitrogen is inert filler that contributes pressure without aiding breathing, but the pressure and temperature must sit inside the bands above. A minimal pure-O2 fill of about 50 kPa at 20-24 C also works (it clears both the 30 kPa device floor and the 16 kPa O2 floor with margin); keep it replenished because the occupant slowly consumes O2 and exhales CO2 into the closed internal volume.

Info panel display bug: the Oxygenation line

The Sleeper info panel "Occupant" block prints Hydration, Nutrition, and Oxygenation via OccupantAtmospherics.AddOccupantString (lines 401205-401223). The Oxygenation line is doubly bugged:

int num = Mathf.RoundToInt(entity.HydrationRatio * 100f);
StringManager.AddKeyValueLine(sb, GameStrings.Hydration, num.ToStringPrefix("%", GetStateColor(num)), indent);
int num2 = Mathf.RoundToInt(entity.NutritionRatio * 100f);
StringManager.AddKeyValueLine(sb, GameStrings.Nutrition, num2.ToStringPrefix("%", GetStateColor(num2)), indent);
int num3 = Mathf.RoundToInt(entity.OxygenationRatio * 100f);
StringManager.AddKeyValueLine(sb, GameStrings.Oxygenation, num2.ToStringPrefix("%", GetStateColor(num3)), indent);

1. Wrong number. The Oxygenation line (line 401216) displays num2, the Nutrition value, not num3, the Oxygenation value. A copy-paste slip. The visible symptom is that the panel's Oxygenation percent always equals its Nutrition percent.
2. Always red. num3 = RoundToInt(entity.OxygenationRatio * 100f), and OxygenationRatio => Oxygenation / 100f (line 283823) where the live Oxygenation reserve is clamped to a maximum of 0.024 (Entity.Oxygenation setter, line 283803). At full health num3 = RoundToInt(0.024) = 0, which GetStateColor maps to red. So the line is red whenever the occupant is alive, regardless of actual oxygen state.

GetStateColor bands (lines 401228-401242):

private string GetStateColor(float percent)
{
    if (percent >= 50f) { if (percent >= 75f) return "green"; return "yellow"; }
    if (percent >= 25f) return "orange";
    return "red";
}

Reading the panel: ignore the Oxygenation line's number and color. To judge whether the occupant is actually oxygenating, read the Occupant Atmosphere block instead (O2 partial pressure should be at least 16 kPa). A powered sleeper fed pure O2 at 100 kPa keeps the occupant's oxygen reserve pegged at its 0.024 maximum and triggers no oxygen damage (the Oxygenation <= 0 damage branch at line 321991 never fires), even though the panel paints "Oxygenation" red. See the corrected scale in ../GameSystems/BreathingAndOxygenation.md.

Verification history

• 2026-06-01: page created from decompiled Assembly-CSharp.dll, game version 0.2.6228.27061. Source lines: Sleeper class 399619-399713 (InitInternalAtmosphere 800 L at 399681, IsOperable 399641, IsSuspendingLife 399670, AssessError/OutputNetwork 399699-399713), OccupantAtmospherics 399413-399618 (limits 399447-399449, IsUnsafeAtmosphere 399457-399478, tooltip "Occupant Atmosphere" 399496-399497, error strings 399503-399537, OnServerTick mode mapping 399592-399601), SpawnPointAtmospherics 401082-401423 (InitInternalAtmosphere 10 L at 401100, stun constants 401086-401088, OnAtmosphericTick mix/stun/heater 401381-401423, _maxHeatKelvin 24 C at 401094), Thing.SetWorldAtmosphere 281183-281202, Human.BreathingAtmosphere 340241-340262. Corrects an earlier sub-agent claim that a sleeper occupant breathes the room: the bed slot is a UseInternalAtmosphere slot, so the occupant breathes the device internal (piped) atmosphere.
• 2026-06-02: added "Info panel display bug: the Oxygenation line" documenting the AddOccupantString bug (line 401216 prints num2/Nutrition instead of num3/Oxygenation; the color from GetStateColor(num3) is always red because OxygenationRatio collapses the 0.024-max reserve to 0). Verified directly and via a fresh validator against decompiled Assembly-CSharp.dll. Cross-references the corrected Oxygenation scale in GameSystems/BreathingAndOxygenation.md.

Open questions

• The bed slot's UseInternalAtmosphere == true is inferred from the coherent behavior of the whole subsystem (internal 800 L atmosphere, IsUnsafeAtmosphere evaluating it, the "Occupant Atmosphere" tooltip rendering it) plus SetWorldAtmosphere's slot branch, rather than read directly off the prefab slot definition. In-game verification via InspectorPlus (snapshot the occupant's WorldAtmosphere reference and compare to the sleeper's InternalAtmosphere) would close this.
• CryoTube specifics (coolant loop via InputNetwork2, ICryogenicRegenerator regeneration behavior, its internal atmosphere volume) were not traced; only that it shares the OccupantAtmospherics base and ILifeSuspender contract.