Air-quality numbers are objective. Air-quality experience is not. Two rooms with identical PM2.5 readings can feel very different if their temperature, humidity, dew point, VOC content, and air velocity diverge. The dashboard's "the feel of air" model integrates the physical parameters into a representation of subjective experience, because that is what users actually report and act on.
The single strongest factor is the combination of temperature and humidity, captured by dew point (see dew point) and apparent temperature (see apparent temperature). At 22 °C and 30% RH a room feels crisp; at 22 °C and 75% RH the same room feels muggy. The dashboard distinguishes both states even when the temperature reading is identical. Fanger's PMV model is the canonical reference for thermal-comfort integration.
VOCs contribute to the subjective experience even at sensor-level-normal values. Sustained VOC index 150 to 200 produces the "stuffy room" sensation many users report even when CO2 is within range. Particulates contribute via mucous-membrane irritation that is more pronounced in dry air. Recent rate-of-change matters too: stepping into a room with 800 ppm CO2 from one at 400 ppm feels "stale" even though 800 is well within normal; the brain reads the gradient.
When the dashboard reports "the air feels off" with no single elevated parameter, the integration is what it is reading. The model takes the seven inputs (T, RH, dew point, VOC, PM, CO2, rate-of-change), runs them through a comfort-experience function, and surfaces the result. Users who report symptoms when the integration crosses a threshold are not imagining things; the parameters are interacting below the individual-threshold level.
References
- ASHRAE Standard 55 - Thermal Environmental Conditions www.ashrae.org
- NOAA NWS - Dew point vs relative humidity www.weather.gov
- Fanger - Predicted Mean Vote thermal-comfort model www.sciencedirect.com
- EPA - Volatile organic compounds and indoor air www.epa.gov
