Indoor CO2 Buildup & Ventilation Interval Calculator
Enter room size and occupancy to see how long until CO2 hits 1,000ppm and how often to air out the room
Based on your room's floor area and number of occupants, calculates how long it takes indoor CO2 to reach the 1,000ppm warning level and how often you should open a window to reset it.
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How to use
- Enter the room's floor area (m²) and the number of people in it.
- See the recommended window-airing interval in minutes.
FAQ
- Why is 1,000ppm the threshold used?
- Above 1,000ppm, people tend to lose focus, feel drowsy, and get headaches, which is why environmental agencies recommend keeping indoor CO2 below that level.
- Does ceiling height affect the calculation?
- Yes — the total volume of air in the room depends on ceiling height as well as floor area, so a room with higher ceilings takes longer to reach the CO2 threshold.
- Does opening a window drop the CO2 level right away?
- Cross-ventilation — opening windows on opposite sides so air actually flows through — can lower it significantly within minutes. Opening just one window slows air exchange, so it takes noticeably longer to clear.