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:
- Resting / sleeping: 0.004 L/min
- Seated work / light activity: 0.007–0.010 L/min
- Standing / light exercise: 0.015–0.025 L/min
- Vigorous exercise: 0.040–0.060 L/min
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. 8 people seated. No ventilation. Outdoor CO₂: 420 ppm. Generation per person: 0.009 L/min = 0.000009 m³/min. After 60 minutes: ΔCO₂ = (8 × 0.000009 × 60) / 90 × 1,000,000 = 0.00432 / 90 × 1,000,000 = 48 ppm × 60 min = 288 ppm rise
Starting at 420 ppm + 288 ppm = 708 ppm — within acceptable range. But without ventilation after 2 hours: ~996 ppm, approaching the performance-impairment threshold.
Solution: Open a window (adds ~3 ACH natural ventilation) to stabilize below 800 ppm throughout the meeting.