The Terrestream sensor reads what is in the room. But the right action (open a window, or seal up) depends on what is outside the window. Two outdoor signals the dashboard cross-references heavily are ozone and pollen.
Ground-level ozone is not emitted directly; it forms when sunlight catalyzes a reaction between NOx and VOCs in the air. That means it peaks on sunny afternoons in summer, and it can be high outdoors when the air looks clean. EPA health-effects data show measurable lung-function impacts at 70 ppb, and asthma exacerbations well below that. On a high-ozone afternoon, opening a window brings the ozone inside.
Pollen behaves seasonally and diurnally. AAAAI notes tree pollen dominates spring, grass pollen early summer, ragweed late summer to first frost. Diurnally, dry-air pollen counts peak in early morning (4 a.m. to 10 a.m.) and again in late afternoon. The sensor sees the resulting PM10 spike whenever pollen drifts indoors.
The dashboard layers outdoor ozone and pollen feeds (from NWS / NOAA and regional reporting) over your indoor sparkline. When outdoor ozone goes red, the "open a window" suggestion auto-suppresses. When pollen is high and your indoor PM10 climbs in lockstep, the dashboard suggests closing windows and running the HEPA filter instead.
References
- EPA - Ground-level ozone basics www.epa.gov
- NOAA / NWS - Air quality and pollen www.weather.gov
- AAAAI - Pollen allergy guide www.aaaai.org
- EPA - Health effects of ozone www.epa.gov
