Carbon Monoxide (CO) Exposure Calculator
Use this quick calculator to estimate your exposure load and risk category based on measured CO concentration and time exposed.
Important: This is an educational estimator, not a medical or emergency diagnostic tool. If you suspect CO exposure, move to fresh air and call emergency services immediately.
What this CO calculator does
Carbon monoxide (CO) is a colorless, odorless gas that can build up indoors from fuel-burning appliances, cars in attached garages, generators, and other combustion sources. This calculator helps you translate two simple inputs—concentration and time—into a practical risk interpretation.
The tool provides:
- Exposure load (ppm·hours): concentration multiplied by duration.
- 8-hour equivalent concentration: a normalized value for easier comparison with common guidelines.
- Risk category and action guidance: lower risk, caution, high risk, or emergency.
How to use the calculator correctly
1) Enter the measured CO value in ppm
Use a reliable CO monitor and enter the reading in parts per million (ppm). If your monitor fluctuates, use a representative average for the period you were in the space.
2) Enter total time exposed
Add the total duration in hours. You can use decimals (for example, 30 minutes = 0.5 hours).
3) Review your risk level and next steps
The result area will summarize your exposure and provide practical recommendations based on generally recognized public-health and occupational ranges.
Understanding common CO ranges
- 0–9 ppm: usually considered a low background range for many indoor settings.
- 10–34 ppm: elevated; prolonged exposure may affect sensitive individuals.
- 35–99 ppm: concerning; headaches and fatigue may appear with continued exposure.
- 100+ ppm: dangerous levels; symptoms can develop faster, especially with longer exposure.
- 400+ ppm: severe danger and potentially life-threatening in short periods.
Why CO is dangerous
CO binds to hemoglobin much more readily than oxygen does, reducing your blood’s ability to carry oxygen to organs and tissues. That oxygen deprivation can cause headache, dizziness, nausea, confusion, loss of consciousness, and in severe cases, death.
Children, older adults, pregnant people, and individuals with heart or respiratory conditions may experience harm sooner at lower concentrations.
If your result is high
Take these immediate actions
- Move everyone to fresh outdoor air immediately.
- Call emergency services if anyone has symptoms (headache, nausea, confusion, chest pain, fainting).
- Do not re-enter the building until it is assessed and declared safe.
- Shut down suspected fuel-burning sources if you can do so safely.
Prevention checklist for homes
- Install CO alarms on every level and near sleeping areas.
- Replace alarm batteries as recommended and test monthly.
- Service furnaces, water heaters, fireplaces, and vents annually.
- Never run a car in an attached garage, even with the door open.
- Never use generators, grills, or camp stoves inside enclosed spaces.
Limitations of this calculator
This calculator uses simplified risk logic for educational planning. Real exposure risk depends on many factors, including concentration changes over time, ventilation, altitude, health status, and whether symptoms are already present.
If you suspect real exposure, prioritize safety over calculations. Get fresh air first, then seek professional medical and emergency guidance.