Second-hand smoke monitoring report

What the pattern shows

Across 31 monitored days, the equivalent of 19 days were free of regional haze; in that time the sensor recorded 305 separate local smoke episodes, about 16.1 a day, each lasting a median of 13 minutes. Every one of the 19 days that were mostly free of regional haze had at least one episode. They follow a daily clock: the first episode typically began around 06:18 and the last around 23:04, with 26% of episodes starting between 6 and 10 AM and 32% between 5 and 10 PM. Weekdays averaged 12.0 episodes a day and weekends 14.6, so the pattern is not tied to a work schedule. 12 days were dominated by regional wildfire smoke and are shown separately; the local episodes are short bursts that rise and fall within minutes, unlike regional smoke, which lifts the whole day. Short, repeated bursts on a daily schedule at a fixed location are the signature of a nearby, deliberate source rather than weather or traffic; the reporter's own observation identifies it as tobacco smoke from an adjacent property.

Calendar: every half hour of the period

Time of day

Share of monitored days (regional-haze days excluded) with a local smoke episode in progress during each hour.

Minutes of local smoke per day

Regional air quality on the same days

Daily maximum of the official regional Air Quality Health Index (Environment and Climate Change Canada, nearest station) beside the local episode count. Local episodes on days when the regional index was low cannot be explained by regional smoke. Regional data has been recorded since 1 October 2026.

Method and limitations

• Instrument. A Plantower PMS5003 laser particle counter, fixed outdoors in the rear yard, sampling every second and averaged over 30 seconds; a Bosch BME688 gas sensor beside it provides an independent smell cross-check (it independently confirmed 48 of the 305 episodes).
• What counts as an episode. Fine-particle (PM2.5) readings jumping above the rolling 30-minute background and staying up for most of a 20-second window, through to the air returning to background for three continuous minutes. Brief dips inside an episode do not end it. Detections whose peak never reached 10 µg/m³ are treated as faint and are not counted as episodes (135 in this period).
• Regional smoke is separated. When the background itself stays elevated for 30 minutes or more (wildfire smoke, fog) the system marks the span as regional; those hours are hatched in the calendar and left out of the local totals. Where available, the official regional index is shown for comparison.
• Limitations. This is a consumer-grade sensor: it shows presence, timing and relative intensity, not regulatory concentrations. The 30-second peaks reported here are not directly comparable with 24-hour guideline values. The instrument does not identify the source of the smoke; that identification rests on the reporter's direct observation.
• Calibration. Detection thresholds were finalised on 18 July 2026; readings before then were recorded with an earlier rule and are noisier.

References

• Health Canada, Second-hand smoke: there is no safe level of exposure to second-hand smoke. canada.ca/en/health-canada/services/smoking-tobacco/second-hand-smoke.html
• World Health Organization, Global Air Quality Guidelines (2021): PM2.5 24-hour guideline 15 µg/m³. who.int/publications/i/item/9789240034228
• British Columbia Air Quality Objective for PM2.5: 25 µg/m³ over 24 hours. www2.gov.bc.ca (Air quality objectives and standards)

Appendix: episode log

Every local episode in the period. Peak is the highest 10-second reading during the episode; background is the typical reading in the ten minutes before it; smell marks episodes the gas sensor confirmed independently. A further 254 detections that began during regional wildfire smoke are not listed. 135 faint detections (peak under 10 µg/m³) are not listed.