Fill in the details and click Calculate to see your results.
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📘 About the Passive Smoking Calculator
Every cigarette releases about 10–14 mg of fine particles (PM2.5) into the air, along with nicotine, carbon monoxide and dozens of cancer-causing chemicals. In a closed room or a car these build up to levels far above even the most polluted city air.
The calculator works out the average smoke level from the room size and air changes per hour, then turns it into cigarettes with the same rule used for air pollution (22 µg/m³ of PM2.5 for a day ≈ 1 cigarette). There is no safe level of second-hand smoke — opening a window or running a fan only reduces it.
✏️ Worked examples
3 cigarettes in a living room, 3 hours, normal ventilation
You get| You "smoke" about | 0.8 cigarettes a day |
| Per week | 5.8 cigarettes |
| Per year | 303 cigarettes |
| Smoke particles in the air (PM2.5) | 147 µg/m³ while you are there |
| Compared with WHO daily guideline | 10× higher |
0.8 cigarettes a day; 303 cigarettes.
2 cigarettes in a car, 1 hour, windows up
You get| You "smoke" about | 2.3 cigarettes a day |
| Per week | 11.6 cigarettes |
| Per year | 602 cigarettes |
| Smoke particles in the air (PM2.5) | 1,222 µg/m³ while you are there |
| Compared with WHO daily guideline | 81× higher |
2.3 cigarettes a day; smoke level 1,222 µg/m³ while you are there.
🧭 How to use this calculator
What you enter
- Where are you exposed?
- Ventilation
- Cigarettes smoked near you (cigarettes)Total smoked by others in the room during the time you are there (count bidis as cigarettes).
- Hours you spend there (h)
- Days a week (days)
What you get
- You "smoke" about
- Per week
- Per year
- Smoke particles in the air (PM2.5)
- Compared with WHO daily guideline
❓ Frequently asked questions
How harmful is passive smoking?
Non-smokers exposed to second-hand smoke have a 25–30% higher risk of heart disease and a 20–30% higher risk of lung cancer (US Surgeon General, 2006). Children get more asthma attacks, ear infections and pneumonia.
Is smoking in a car with the window open safe?
No. A cigarette in a car can push fine-particle levels to hundreds of µg/m³ even with a window partly open — many countries ban smoking in cars with children.
Does an air purifier remove second-hand smoke?
A HEPA purifier removes some particles but not the gases. The only way to protect others is to smoke outside, away from doors and windows, or to quit.