Where do the numbers come from?

Every number on the dashboard belongs to one of four classes. Device-direct sensor readings come from a physical channel on the Sensirion SEN66, the Bosch BMP390L pressure sensor, or the TI OPT3001 lux sensor. PM₁, PM_2.5, PM₄, PM₁₀, CO₂, raw temperature, relative humidity, pressure, and lux are all direct.

Device-derived computations are functions of one or more direct readings. The IAQ index (the worse of the PM_2.5 and PM₁₀ sub-indices) and the VOC and NOₓ Sensirion indexes (which are themselves derived from raw MOX conductance against a rolling baseline) live here. Terrestream also calculates the dew point (from RH and T), absolute humidity and cross-room comparisons behind the scenes. Comparisons with a room's usual levels need a few days of data after install before they mean much.

The Google Air Quality API and Open-Meteo's air-quality model supply the outdoor pollutant fields: outdoor PM_2.5 and PM₁₀, NO₂, SO₂, ozone, CO, and the US EPA AQI bands, with pollen coming from the Google Pollen API. These are regional estimates; they are not your block, and on a fast-moving event (a smoke plume edge passing through, a sudden wind shift) the dashboard may see your indoor PM track outdoor changes faster than the API can report them.

Open-Meteo Forecast (ECMWF) supplies the weather context: outdoor temperature, humidity, dew point, wind, precipitation, pressure, cloud cover, UV index, solar radiation. These are forecast or analysis values, useful for predicting what indoor conditions will face over the next 24 hours. The interpretation layer uses all four classes together: a sensor spike with no outdoor support is an indoor source; an outdoor spike with no indoor support is a working envelope.