Indoor CO₂ PPM Checker
That 3 PM office slump might be CO₂, not lunch. Under 1,000 PPM feels fresh; 1,000–2,000 gets stuffy; above 2,000 measurably dulls thinking. Enter your monitor reading.
Calculator
Indoor CO₂ PPM Checker
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That 3 PM office slump might be CO₂, not lunch. Under 1,000 PPM feels fresh; 1,000–2,000 gets stuffy; above 2,000 measurably dulls thinking. Enter your monitor reading.
How to use this calculator
- Enter indoor CO₂ PPM.
- See the comfort band.
- Get ventilation fixes.
The formula
Bands from indoor-air-quality research.
What the units mean
PPM (parts per million) — one part of solute per million parts of the total mixture. The workhorse unit for trace concentrations in water, air, and food.
Worked example
Bedroom overnight: 1,800 PPM → crack a window or run ventilation; sleep quality suffers above ~1,500.
Quick reference
| CO₂ | Feeling |
|---|---|
| <800 PPM | Fresh |
| 800–1,200 | OK |
| 1,200–2,000 | Stuffy |
| >2,000 | Drowsy — ventilate |
Steady-state readings.
Where you will actually use this
CO₂ is the easiest indoor-air metric to measure and fix.
- Offices
- Classrooms
- Bedrooms
- Meeting rooms
Mistakes that give wrong answers
- Blaming the HVAC when windows would do
- Measuring next to a person's breath
Key takeaways
- Formula: Indoor CO₂ comfort and cognitive bands
- Remember: Steady-state readings.
- Watch out for: Blaming the HVAC when windows would do
- Next step: run your own numbers in the calculator above, then verify with a measurement — calculated values are only as good as the inputs.
Frequently asked questions
What is a good indoor CO₂ level?
Under 1,000 PPM; outdoor is ~420.
Does high CO₂ make you sleepy?
Yes — drowsiness and poor concentration start around 1,500–2,000 PPM.