CO₂, temperature and humidity at a glance — with color indicators that show when a room may need fresh air
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Indoor air changes through the day — and it's hard to tell by feel alone.
Every breath adds carbon dioxide. In a closed room without much ventilation, levels can rise over a few hours.
You can't see or smell carbon dioxide. Chart is an illustrative example — actual levels depend on room size, number of people and ventilation.
A monitor shows you the number, so you know when to let fresh air in.
The display shows when CO₂ rises.
Open a window, and watch the reading come back down.
Stale air
Let in fresh airOpen a window
Fresh air
Illustrative readings. Results vary by room, occupancy and outdoor air.
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Everything that affects how you feel at home.
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Not reliably. You can’t see or smell carbon dioxide, and people tend to get used to a room’s air gradually. A monitor gives you a number instead of a guess.
Not necessarily. Older homes often leak a little air around windows and doors. A tightly sealed home is more energy-efficient, but it may also need more deliberate ventilation — a monitor helps you see whether yours does.
It can. Seirun measures CO₂, which people breathe out indoors, so levels can rise in a closed room regardless of outdoor air quality. Seirun does not measure outdoor pollutants, particles or mold.
Outdoor air is typically around 420 ppm. Under about 1,000 ppm is commonly used as a guideline for well-ventilated indoor spaces; higher readings suggest the room could use fresh air. You don’t need to remember the numbers — the screen shows green, yellow or red.
No. Just plug it in and it starts working right away. No app to download, no account, no wifi to connect.
Yes. Moving it between rooms is a simple way to see which ones may need more ventilation.
No. Seirun is a consumer monitor that displays CO₂, temperature and humidity. It does not purify air, remove mold, or diagnose, treat or prevent any health condition. If you have ongoing symptoms, please speak to a doctor.
See your CO₂, humidity and temperature at a glance, so you know when it's time to let fresh air in. Backed by our 30-day money-back guarantee.
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