Smog Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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Benzo[a]pyrene is one component of combustion-related air pollution, and inhaled dose depends on concentration as well as time spent indoors and outdoors. This calculator turns an ambient concentration into an annual inhalation illustration, then expresses that mass as a cigarette-equivalent comparison for scale—not as a smoking or cancer-risk equivalence.

What this calculator does

The Smog Calculator uses a custom or limited reference concentration, hours spent outside, an adult inhalation approximation of 0.83 m³/hour, a 10% lower indoor concentration assumption, and 14.86 ng B[a]P per cigarette. It reports weighted air inhaled per day, annual nanograms inhaled, and cigarette equivalents per year.

How to use it

Choose a location preset or enter a custom B[a]P concentration in ng/m³, then enter hours spent outside per day. The calculator assigns the remaining hours to indoors and applies its 90% indoor-concentration factor. Use a concentration that represents the exposure period and location you are investigating; a single annual-average monitor value may not match personal exposure.

How the calculation works

Weighted air volume = 0.83 × [outside hours + 0.9 × indoor hours] m³/day, where indoor hours = 24 − outside hours. Annual B[a]P inhaled = concentration × weighted air volume × 365. Cigarette equivalents = annual nanograms ÷ 14.86 ng per cigarette.

Example

At 1 ng/m³ and 2 hours outdoors per day, the weighted inhaled air volume is about 18.09 m³/day. Over 365 days, the calculator estimates about 6,604 ng of B[a]P. Dividing by 14.86 ng per cigarette gives roughly 444 cigarette equivalents under this specific mass-comparison model.

How to interpret the result

The cigarette-equivalent number is only a way to compare one pollutant mass with the calculator’s per-cigarette B[a]P factor. It does not mean breathing the modeled air has the same total toxic exposure or health risk as smoking that number of cigarettes. The underlying annual ng value is the cleaner quantity for understanding what the model actually calculates.

Limitations and notes

Personal inhalation varies with age, activity, ventilation, filtration, building infiltration, indoor sources, commuting, and day-to-day pollution. B[a]P is only one pollutant, and cancer risk requires a separate validated risk-assessment framework. The preset location options are limited reference scenarios; this calculator is an exposure illustration, not an individual diagnosis or cancer-risk estimate.