If you place a CO2 monitor in the bedroom in the evening, you will often see the reading rise significantly within an hour. This is no coincidence or a faulty monitor; it is simply a matter of calculation: a small, enclosed space, two people breathing, and little to no fresh air coming in.
A bedroom is relatively small and usually closed
Most bedrooms are not large, and at night most people close the door and the window at least partially. This leaves you with an almost enclosed volume of air. There is simply little air present to dilute the CO2, and hardly any supply of fresh air from outside to compensate for that.
Two people exhale CO2 for eight hours
A sleeping person exhales about 15 to 20 times per minute, and each breath contains higher CO2 levels than the air that is inhaled. With one person in an average bedroom, the reading already rises, but with two people (or a child with them), it happens about twice as fast. If you calculate this over seven or eight hours of sleep, it is no wonder that the reading can rise from around 450 ppm at bedtime to 1,500 ppm or more by morning.
Little natural ventilation at night
During the day, a house often ventilates implicitly: doors open and close, people walk around, a window is occasionally opened. At night, this almost completely disappears. Even a home with ventilation grilles that seem sufficient during the day can still show a buildup of CO2 in the bedroom at night, simply because the grilles are smaller than the amount of air needed to keep up with two breathing people.
Why you notice this as a stuffy feeling
An elevated CO2 level in the bedroom is recognized by many people in the morning as a stuffy, drowsy, or sluggish feeling, sometimes with a slight headache. This is not dangerous poisoning at the levels that occur in an ordinary bedroom, but it contributes to a less invigorating night's sleep for many people, especially above 1,000 to 1,500 ppm.
What helps: slightly more air exchange, not necessarily more air movement
The solution lies in actual air exchange: a window slightly ajar, a ventilation grille left open, or the bedroom door slightly ajar so that air can flow out from the rest of the house. A fan alone does not solve this; it moves the air in the room but does not add fresh air from outside (you can read more about this in our article about fans and CO2).
This is not a topic for which Dynter sells a device
Ventilation and CO2 are topics for which we deliberately do not push our own product: Dynter does not sell CO2 monitors or mechanical ventilation systems. If you do want to measure how bad it is in your bedroom, a CO2 monitor with an NDIR sensor is the best first step. For other aspects of a healthy bedroom, such as a quiet fan for warm nights, you can visit dynter.eu.