Living room · near plants · San Francisco

ROOM
TONE.

A CO₂ monitor on the shelf took 42058 readings, one every 5 minutes for 147 days. I compare them with the San Francisco air outside. The median CO₂ is a fresh 550 ppm. The climate of the room follows the city almost exactly

The data comes from an Aranet4 CO₂ monitor indoors, with Open-Meteo weather and air-quality archives for San Francisco

As of 17 Oct 2026 11 days old

Median CO₂ 550 ppm · 97.3% under 800
Room temp 72.6 °F · 52.9% humidity
Outside, period average 60.9 °F · AQI 48
Tracks SF pressure 1.00 correlation · pressure passes through walls

The Room's Day

Average CO₂ by hour. It rises slowly overnight and peaks at about 684 ppm at breakfast, when the apartment is closed and everyone is home. Then it falls all afternoon as the windows open. It reaches its lowest point near 492 ppm

600 · fresh 12a 6a 9a 12p 4p 6p 11p

Indoor vs SF

This shows how each indoor reading correlates with the outdoor value in San Francisco. Pressure is identical, because it passes through walls. This also confirms that the sensor really is here. Temperature and humidity follow the city, but the building reduces the changes. CO₂ does not follow the outdoor warmth

Air pressure 1.0
Humidity 0.8
Temperature 0.84
CO₂ vs outdoor warmth -0.01

−1 inverse0+1 in step

Room Holds, City Swings

Indoor and outdoor temperature, every day. The green line is the living room, with a mean of 72.6°F. The blue line is San Francisco outside. The shaded gap shows the effect of the building. On average it keeps the room 11.8° warmer. The daily mean has a range of 16.7° indoors and 19.4° outside

60° 70° 80° 2026-05-24 2026-10-17
Living room Outside · San Francisco

Across The Season, And Who's Home

Daily average CO₂ from May into October. It goes down slowly as spring gets warmer and the windows stay open in summer. The strip below shows occupancy. In an empty flat, CO₂ falls to baseline and stays flat. So a flat, low day means that nobody is home. Flights explain the blue spans. No flight explains the one orange mark

600 OCCUPANCY 06-20 2026-05-24 2026-10-17
Home · 131d Away, flight · 15d Away, no flight · 1d
Caught by the CO₂

Every empty period matches a flight, except one. Saturday 20 Jun 2026 stayed at baseline (about 473 ppm), but I logged no trip. The flat emptied on Friday afternoon and stayed empty until Sunday evening. It was a weekend away that my flight log never recorded

Does It Touch My Health?

Indoor readings compared with Garmin daily metrics, with travel days removed. The links are real, but look at the direction. More CO₂ goes with less stress and better recovery. That is the opposite of what "bad air" would do. Indoor CO₂ is really a marker of home-and-resting vs out-and-active

Living-room temp → Resting HR -0.26
Outdoor PM2.5 → Steps -0.21
Living-room temp → Sleep -0.18
Night humidity → Resting HR -0.18

−1 inverse0+1 in step

The confound, in numbers
Day type (by CO₂)StepsStressRecovery floor
Low CO₂ (out / ventilated)1086725.623.6
Mid1020325.623.8
High CO₂ (home / closed)1002425.524.0

Low-CO₂ days are the busy days away from home. They have more steps, more stress and a lower recovery floor. The air did not cause that. My schedule did

What CO₂ does not move Sleep · Resting HR

Neither shows a significant link to indoor CO₂. In this healthy range, CO₂ in the room does not appear to change sleep length or cardiac recovery. Room temperature and humidity do show weak links to them, up to |r| = 0.26, in the list above. These are associations only, n = 146 days