Secondhand Air

Breathing a full day of polluted air can equal smoking actual cigarettes. Secondhand reads the PM2.5 where you are and converts it into the only unit everyone understands. TODAY — one big number: how many cigarettes today's air is worth, with a 24-hour forecast so you know when it clears. LOG — your season, tracked automatically. Packs filled, daily heatmap, worst day. PLACES — save cities, compare their air. "12× more smoke in Boise. Drive north." ALERTS — set your line in cigarettes, not AQI. One notification when the day crosses it. Plus a calculator: going out 2 hours = how many cigarettes? ASHCASH — flip it around. If you actually smoke, see what quitting buys back: money per week, year, decade — and days of life regained. Data from the EPA AirNow monitor network and the Open-Meteo air quality model. Everything stays on your phone: no accounts, no tracking, nothing leaves the device. Conversions are estimates for awareness (1 cigarette ≈ 22 µg/m³ PM2.5 over 24h, Berkeley Earth; ~20 minutes of life per cigarette, Jackson et al. 2024), not medical advice.