A healthy CO2 level indoors is generally below 800 to 1000 ppm (parts per million). Outdoor air is around 420 ppm, and the further above that you get indoors, the less effectively a room is ventilated.
What CO2 levels exactly mean
CO2 (carbon dioxide) is released by everything that breathes: people, pets, and also by combustion, such as a gas stove or candle. In a well-ventilated room, that CO2 is continuously replenished with fresh outdoor air, keeping the level low. In an enclosed room, CO2 accumulates, and the concentration acts as a practical indicator of how much "used" air is hanging in a room.
The ppm scale in broad terms
A few guidelines that are often used to indicate CO2 levels:
- Up to 800 ppm: good ventilation, this is considered healthy.
- 800 to 1000 ppm: acceptable, but a sign that extra ventilation wouldn't hurt.
- 1000 to 1500 ppm: moderate, many people notice this as a heavier or less fresh feeling in the room.
- Above 1500 ppm: insufficient ventilation, structural ventilation is then recommended.
Why this is mainly about ventilation
A high CO2 level is almost always caused by insufficient air exchange, not by polluted outdoor air or a specific appliance in the home. The only thing that structurally lowers CO2 is letting fresh air from outside in: through a window, a ventilation grille, or a mechanical ventilation system. Appliances that purify or dehumidify the air, such as an air purifier, have no effect on the CO2 level: they filter particles or moisture, but do not replace fresh air.
How to monitor this yourself
If you want to know how things stand in your bedroom, living room, or home office, a CO2 meter gives the clearest picture. Dynter does not sell this type of measuring equipment, so we honestly cannot recommend our own product in that regard. Instead, pay attention to practical signs: a musty smell, fogged-up windows, or a sluggish feeling after an hour in an enclosed room often already indicate a CO2 level that is too high.
In short: aim for a CO2 level below 1000 ppm by ventilating regularly, especially in bedrooms and smaller rooms with multiple people. For other aspects of a healthy indoor climate, such as moisture and fine dust, look at dynter.eu.