Living room · near plants · San Francisco

ROOM
TONE.

32155 readings from a CO₂ monitor on the shelf, every 5 minutes for 113 days — held up against the San Francisco air outside. Median CO₂ sits at a fresh 591 ppm, and the room's climate shadows the city almost perfectly.

Source: an Aranet4 CO₂ monitor indoors, paired with Open-Meteo weather and air-quality archives for San Francisco.

Median CO₂ 591 ppm · 91.3% under 800
Room temp 70.5 °F · 50.9% humidity
Outside now-ish 58.6 °F · AQI 49
Tracks SF pressure 1.00 correlation · walls don't stop weather

THE ROOM'S DAY.

Average CO₂ by hour. It creeps up overnight and peaks around 733 ppm at breakfast (apartment closed, everyone home), then falls all afternoon as windows open and the plants photosynthesise — bottoming near 522 ppm.

600 · fresh 12a 6a 9a 12p 4p 6p 11p

INDOOR
vs SF.

How each indoor reading correlates with the outdoor value in San Francisco. Pressure is identical (it passes through walls — a neat proof the sensor really is here). Temperature and humidity follow the city, damped by the building. And CO₂ drops on warm days: windows open.

Air pressure 1.0
Humidity 0.81
Temperature 0.74
CO₂ vs outdoor warmth -0.37

−1 inverse0+1 in step

ROOM HOLDS,
CITY SWINGS.

Indoor vs outdoor temperature, every day. The green line is the living room, holding near 70.5°F; the blue line is San Francisco outside, ranging over 19.1°. The shaded gap is the building doing its job — on average it keeps the room 11.9° warmer and far steadier (11.7° indoor spread vs 19.1° outside).

60° 70° 2026-03-28 2026-07-18
Living room Outside · San Francisco

ACROSS THE SEASON
— AND WHO'S HOME.

Daily average CO₂ from late March into July, drifting down as spring warms into an open-window summer. The strip beneath reads occupancy: an empty flat decays to baseline and flatlines, so a flat-low day means nobody's home. Blue spans are explained by flights; the lone orange mark is not.

600 800 OCCUPANCY 06-20 2026-03-28 2026-07-18
Home · 92d Away, flight · 20d Away, no flight · 1d
Caught by the CO₂

Every empty stretch lines up with a flight — except one. Saturday 2026-06-20 sat at baseline (~473 ppm) with no trip logged: the flat emptied Friday afternoon and didn't stir until Sunday evening — a weekend away the airfare never recorded.

DOES IT TOUCH
MY HEALTH?

Indoor readings vs Garmin daily metrics, travel days removed. The links are real — but read the direction: more CO₂ goes with less stress and better recovery. That's backwards for "bad air," because indoor CO₂ is really marking home-and-resting vs out-and-active.

Night humidity → Steps -0.48
Overnight CO₂ (home) → Stress -0.33
Overnight CO₂ (home) → SpO₂ 0.33
Overnight CO₂ (home) → Body-battery min 0.32
Daytime CO₂ → Stress -0.32
Daytime CO₂ → SpO₂ 0.32
Daytime CO₂ → Body-battery min 0.32
Daytime CO₂ → Steps -0.3
Living-room temp → Steps 0.28
Overnight CO₂ (home) → Steps -0.25
Living-room temp → SpO₂ -0.21
Outdoor PM2.5 → Stress 0.21
Outdoor PM2.5 → SpO₂ 0.2

−1 inverse0+1 in step

The confound, in plain view
Day type (by CO₂)StepsStressRecovery floor
Low CO₂ (out / ventilated)1176529.419.2
Mid922826.823.4
High CO₂ (home / closed)970226.823.2

Low-CO₂ days are the busy, out-of-the-house ones — more steps, more stress, a lower recovery floor. The air didn't cause that; the calendar did.

What the air does not move Sleep · Resting HR

Neither shows any significant tie to indoor CO₂, temperature or humidity (all |r| under 0.13). In this healthy range, the room's air leaves sleep length and cardiac recovery untouched — a reassuring null. Associations only; n = 102 days.