Doctor reveals why keeping your bedroom door ajar at night helps you sleep deeper and for longer

Question: do sleep with your bedroom door open or closed at night? If you shut it, and you're constantly waking up through the night, then leaving it open instead could be the instant solution to your frequent wake-ups.

Yes, scientists are saying that sleeping in an unventilated room leads to an increase in levels of carbon dioxide (CO₂), which leads to broken and disrupted sleep.

To learn more, I spoke to mold and air quality expert and founder of HomeCleanse Michael Rubino, and to Dr. William Lu, MD, a sleep medicine physician.

Here these certified experts explain what happens to the air we breathe when we're sleeping in an unventilated room, and what that means for our sleep.

Key takeaways

• Experts maintain that sleeping with your bedroom door won't lead to CO₂ poisoning
• However, sleeping in an unventilated bedroom can cause CO₂ levels to rapidly increase, leading to sleep disturbances
• Cigarette smoke, candles and incense sticks also release CO_2, contributing to rising levels of the gas

A closed door turns your bedroom into its own air bubble

Here in the northern hemisphere it’s the middle of winter, which often means freezing nighttime temperatures. So it makes sense to close up your windows and doors in a bid to stay cozy at night.

However, by removing the ventilation in your bedroom you are effectively creating a CO₂ bubble, warn experts. That’s because when we breathe, we breathe in oxygen and exhale CO₂.

"If the bedroom door is closed, you’re usually cutting down air exchange," explains Michael, who is also Chair of the Change the Air Foundation, a non profit organization that promotes safer indoor air quality for everyone.

"The bedroom becomes its own little 'air bubble.' That matters because the air in that room changes over the night," says Michael. "You’re exhaling CO₂ for hours."

As well as increased levels of CO_2, moisture from your breath builds up, which can lead to mold growth (investing in one for the best dehumidifiers will help with this).

Plus, any VOCs from furniture, bedding, fragrances, candles, cleaning residues will linger for longer in a closed room, with evidence suggesting that this, along with rising CO₂ levels, can also impact sleep quality.

As the source of increasing levels of CO₂ is our breathing, levels can rise quicker than we expect, especially over the course of a night's sleep,says Michael. The size of your bedroom and the number of people sleeping in it can also impact the rise that CO₂ rises.

There is some research to suggest that overnight CO₂ levels can land in the 1,620 to 3,300ppm range under low-ventilation conditions. However, these levels are show to drop below 1,000ppm when ventilation is increased.

Michael emphasizes that the levels of CO₂ indicated above aren't cause for alarm, but they should prompt you to improve your air circulation.

"Just to be clear, the CO₂ levels we’re talking about in most bedrooms aren’t 'you’re being poisoned,'" says Michael. "CO₂ is mainly a clue. If it’s high, it usually means the room isn’t getting enough fresh air for the number of people breathing in it."

Why keeping your bedroom door closed can wake you up at night

Closing the bedroom door behind you is probably one of the last things you do before climbing into bed. However, sleeping in an unventilated bedroom leads to increased levels of CO₂, which scientific research indicates can disturb your sleep.

“When carbon dioxide levels increase, our sleep often becomes lighter and more fragmented,” explains Dr Lu, a Medical Director at digital sleep clinic Dreem Health.

“You are not likely to have trouble falling asleep, but it is likely you will get less deep, restorative sleep."

Studies suggest that increased levels of CO₂ in the air can translate to higher levels of CO₂ in our bloodstream.

“As there is an element of carbon dioxide homeostasis in our bodies, the response to the carbon dioxide elevation can be less deep sleep, more light sleep, and more awakenings,” continues the sleep medicine physician.

In contrast, sleeping in a well ventilated bedroom means you can achieve deeper, more restful sleep, with fewer bouts of waking up at night.

“A well-ventilated bedroom helps keep our carbon dioxide levels steady and supports the body’s carbon dioxide homeostasis level,” says Dr Lu. “This becomes an improved environment conducive to more restorative sleep.”

How to reduce CO2 levels in your bedroom

Opening your bedroom door or window, even just ajar to allow in a steady flow of fresh air, is the obvious step to improving the ventilation of your bedroom.

However, as Michael acknowledges, that's not always an option for everyone. "A closed door can be a fire safety benefit. So I don’t treat this like 'door open is always best.' I treat it like: if you sleep with the door closed, you should be more intentional about how the room gets fresh air," he explains.

With that in mind, here’s three other ways to reduce CO₂ levels of your bedroom for better sleep.

1. ‘Burp’ your bedroom before bed

Bedroom burping is a slightly repulsive term but essentially describes the practice of ventilating your bedroom for a 5-10 minute period. In Germany, they call this practice ‘luften’, which means to air out.

Regardless of what you call it, opening your bedroom window wide before going to bed, even in the middle of winter, allows fresh air to flood your bedroom and forces stale air to leave.

Pockets of shock ventilation like the above is especially important during the winter months, during which time most of us have our bedrooms sealed tight for warmth. This results in CO₂ levels rising throughout the day.

2. Avoid lighting candles

CO₂ levels increase steadily while we sleep, as we exhale it when breathing. However, there are other contributors of rising CO₂ levels in the bedroom, which includes any product or appliance that burns fuel.

These could be candles or incense sticks, which release CO₂ when burnt. What’s more, these products likely contain harmful volatile organic compounds (VOCs), which can harm your respiratory health.

"Plug-ins, heavily scented sprays, candles, incense, even strong laundry fragrance sitting in bedding. If someone is already sleeping poorly and the room is under-ventilated, adding more scent or smoke is not doing them any favors," says Michael.

So, unless you can open your door or window while burning them, hold off on the candles and incense sticks before bed.

3. Don't seal off your bedroom from airflow

In order to keep CO₂ levels down while you sleep, air needs to be able to move in and out of your bedroom. Opening the door or window, even just a crack, provides much needed ventilation.

If security is an issue, consider a door chain for safety. Or, alternatively, look at products such as a window restrictor. These lock your window open but at a reduced angle.

"If the door stays closed, fine. Just make sure the room still has a way to move air," concludes Michael.

"Sometimes that’s simple clearance under the door. Other times it’s a properly designed transfer opening. The point is not the hardware. The point is that air has to be able to move through the room, not just sit in it."

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