CO2 in Room Calculator
Estimate CO2 levels in a room based on volume, occupants, and ventilation rate.
Check if your indoor air quality is healthy.
CO₂ concentration in a room rises when people breathe and falls when fresh air is supplied. Measuring and managing indoor CO₂ levels directly affects cognitive performance, alertness, and health — making it critical for offices, classrooms, and sleeping spaces.
CO₂ accumulation formula: ΔCO₂ (ppm) = (Occupants × CO₂ Generation Rate × Time) / Room Volume × 1,000,000
CO₂ generation rates per person (roughly):
- Resting / sleeping: ~0.2 L/min
- Seated work / light activity: ~0.3 L/min
- Standing / light exercise: ~0.5–0.8 L/min
- Vigorous exercise: ~1.5–2.5 L/min
This calculator uses about 0.3 L/min, the standard figure for a seated adult.
Room CO₂ level formula (with ventilation): Steady-State CO₂ = Outdoor CO₂ + (Occupants × Generation Rate) / Ventilation Rate
Where Ventilation Rate = air changes per hour (ACH) × Room Volume.
CO₂ thresholds and effects:
| CO₂ Level (ppm) | Classification | Effect |
|---|---|---|
| 400–600 | Outdoor / fresh air baseline | Optimal cognitive performance |
| 600–1,000 | Acceptable (ASHRAE standard) | Minor drowsiness in some people |
| 1,000–1,500 | Elevated | Measurable decline in decision-making (Harvard study: ~15% impairment) |
| 1,500–2,500 | High | Headaches, fatigue, difficulty concentrating |
| 2,500–5,000 | Very high | Significant cognitive impairment, possible nausea |
| > 5,000 | Dangerous | Workplace limit; oxygen displacement risk |
Worked example: Conference room: 6 m × 5 m × 3 m = 90 m³ (90,000 L). 8 people seated. No ventilation. Outdoor CO₂: 420 ppm. Generation per person: about 0.3 L/min. After 60 minutes:
- CO₂ added = 8 people × 0.3 L/min × 60 min = 144 L
- Rise = 144 L ÷ 90,000 L × 1,000,000 = 1,600 ppm
- Room CO₂ = 420 + 1,600 = about 2,020 ppm
That is well into the “high” band, where headaches and poor concentration set in. A packed room with no fresh air climbs fast.
Solution: Open a window or run mechanical ventilation. Even a few air changes per hour pulls a room like this back toward 800–1,000 ppm.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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