Yes, plants do release CO2 at night as a natural part of their respiration process, but this is a normal biological function and not a cause for concern. During the night, photosynthesis stops due to the lack of sunlight, while cellular respiration continues 24/7. The amount of CO2 emitted at night is very small and does not pose any health risk to people or pets sharing the same room.
Why do plants release CO2 at night?
Plants release CO2 at night because of a process called
cellular respiration. This is how all living organisms—plants, animals, fungi, and bacteria—convert stored energy (sugars) into usable energy (ATP) to power their cells. In plants, respiration is always happening, day and night. During the day, plants also perform
photosynthesis, which uses sunlight to convert CO2 and water into sugars and oxygen. Because photosynthesis produces much more oxygen than respiration consumes, the net effect during daylight is a release of oxygen. At night, without sunlight, photosynthesis stops, but respiration continues, so the plant uses oxygen and releases CO2.
Think of it like breathing for people. You breathe in oxygen and breathe out CO2 all day and night. A plant's respiration is like its own steady, quiet breathing—tiny, continuous, and essential to life.
Is it harmful to sleep with plants in your bedroom?
No, it is
not harmful to sleep with plants in your bedroom. The amount of CO2 a typical houseplant produces at night is extremely small compared to the volume of air in a room. For context, a single person breathing all night produces far more CO2 than dozens of houseplants combined. The slight increase in CO2 from a few plants is not enough to cause any health issues, headaches, or problems with sleep quality.
In fact, many people find that having plants in their bedroom improves mood, reduces stress, and can even help with humidity levels. A few popular bedroom plants like snake plants, spider plants, and aloe vera are often cited as "good for bedrooms" because they also perform a type of photosynthesis called
CAM photosynthesis (Crassulacean Acid Metabolism), which allows them to take in CO2 at night and store it for use during the day. However, even plants that don't use this method are perfectly safe.
What is the difference between respiration and photosynthesis?
It helps to understand how a plant's two main gas-exchange processes work:
- Photosynthesis (happens only in daylight): Uses sunlight, water, and CO2 to produce sugars and oxygen. This is the process that feeds the plant and releases oxygen into the air.
- Respiration (happens 24/7): Uses oxygen and sugars to produce energy for the plant, releasing CO2 and water as byproducts. This is the plant's "metabolism" and keeps its cells alive.
During the day, photosynthesis is much more active than respiration, so the plant
absorbs more CO2 than it releases. At night, only respiration occurs, so the plant releases a small amount of CO2. The important thing to remember is that over a full 24-hour cycle, a healthy plant is
a net absorber of CO2—it takes in more than it gives off.
Do all plants release the same amount of CO2 at night?
Not exactly. The amount of CO2 a plant releases at night depends on several factors:
- Size of the plant: A large, leafy plant like a fiddle-leaf fig will release more CO2 than a small succulent because it has more living tissue that needs energy.
- Growth stage: Actively growing plants respire more than dormant or slow-growing ones.
- Temperature: Warmer temperatures increase respiration rates, so a plant in a warm room may release slightly more CO2 than one in a cool room.
- Plant type: As mentioned, some plants (like orchids, succulents, and cacti) use CAM photosynthesis, which reduces the amount of CO2 released at night because they store it during the night for use during the day.
Despite these variations, even the largest houseplant's nighttime CO2 output is very small—less than 0.1% of what a human produces by breathing. You would need hundreds of plants crammed into a sealed, tiny room to notice any meaningful change in CO2 levels.
How much CO2 does a houseplant actually produce at night?
Here is a simple comparison to show how tiny a plant's CO2 output really is. This table uses rough averages for a medium-sized houseplant in a 100-square-foot bedroom with standard ceiling height:
| Source | CO2 Produced (approximate per hour) |
|---|
| One small hanging planter (e.g., pothos) | 0.001 grams |
| One medium snake plant (12-inch pot) | 0.002 grams |
| One human at rest | 30–40 grams |
| A typical air freshener spray (one squirt) | ~0.5 grams |
As you can see, the plant's contribution is minuscule. Even 50 plants in a room would still produce less CO2 than a single person.
Can plants improve indoor air quality despite nighttime CO2?
Yes, and this is the bigger picture. While plants do release a tiny amount of CO2 at night, their overall effect on indoor air quality is
positive. Through photosynthesis during the day, they absorb CO2 and release oxygen. They also help remove certain airborne pollutants like benzene, formaldehyde, and xylene through their leaves and roots, a process often called
phytoremediation.
That said, it takes many plants to make a significant difference in air purification for an entire room. One or two plants in a bedroom are great for mood and humidity, but you might need a dozen or more for measurable air-cleaning benefits. If you want to maximize the air-purifying potential of your indoor garden, consider adding a portable
air quality monitor to track CO2 levels and other pollutants. A simple monitor can help you see that even with several plants around, your CO2 levels remain healthy and safe.
Check out popular indoor air quality monitors on Amazon for a helpful tool to measure your room's air (available in various price ranges).
Does this mean plants compete with humans for oxygen at night?
This is a common myth, but the answer is no—not in any meaningful way. The tiny amount of oxygen used by a plant at night for respiration is vastly outweighed by the oxygen it produces during the day. Over a 24-hour period, a plant is a net oxygen producer. The idea that plants "steal oxygen" at night is based on misunderstanding the scale of respiration.
Think about this: A single tree can produce enough oxygen in one day to support two people. Meanwhile, its nighttime respiration uses only a small fraction of that oxygen. The same is true for houseplants. They are not competing with you for breathable air. They are living organisms that quietly contribute to a healthier environment.
What about plants in a sealed terrarium or closed space?
In a completely sealed environment—like a closed terrarium, a greenhouse with no ventilation, or a plant-filled van—the CO2 produced at night can accumulate. This is why sealed terrariums usually have small openings or are occasionally opened to refresh the air. But in a normal home or bedroom with any air exchange (even a tiny gap under the door), the CO2 from plants is diluted and becomes undetectable.
If you keep plants in a very small, airtight room without any ventilation, you would notice a rise in CO2 from
your own breathing long before the plants' contribution matters. The best way to keep any room fresh is to open a window or use a fan, which quickly disperses CO2 and brings in fresh air.
What are the best plants for a bedroom?
If you are still worried about CO2 at night, or you just want plants that are especially efficient, consider these popular choices that use CAM photosynthesis (they take in CO2 at night and store it):
- Snake plant (Sansevieria): Extremely low-light tolerant and releases oxygen at night.
- Aloe vera: Also releases oxygen at night and has medicinal gel in its leaves.
- Orchid: Many varieties use CAM and add beauty to any room.
- Spider plant: Easy to care for and great at removing formaldehyde.
- Peace lily: Known for its air-purifying abilities and lovely white flowers.
All these plants are safe, easy to care for, and will not cause any CO2 issues.
Should I remove plants from my nursery or child's room?
No, there is no need to remove plants from a child's room. In fact, plants can help teach children about nature and provide a calming presence. The tiny amount of CO2 emitted is not a health concern. Just make sure the plants are non-toxic if a child might try to eat the leaves. Snake plants and peace lilies, for example, are mildly toxic if ingested, so keep them out of reach. For a nursery, consider safe, non-toxic options like the
areca palm,
Boston fern, or
prayer plant.
You can also look for a
plant care guide book to help you choose the best, safest plants for your family's home.
Browse beginner-friendly houseplant care books on Amazon for helpful tips on choosing and maintaining safe indoor plants.
One simple checklist for sleeping with plants
If you want to keep plants in your bedroom and feel totally at ease, here is a quick checklist:
- Choose small to medium-sized plants (one or two per room is plenty).
- Ensure the room has basic air exchange (a normal bedroom door or window gap is enough).
- Keep plants at least a few feet away from your face and pillows.
- Water plants in the morning, not at night, to avoid damp soil odors.
- Pick low-light tolerant varieties if your bedroom has no direct sun.
- Enjoy the mood boost and cleaner daytime air your plants provide.
Do outdoor trees and gardens emit noticeable CO2 at night?
Yes, but just like houseplants, the effect is not something humans can detect. A large tree can release a measurable amount of CO2 at night, but it is diluted by the vast volume of outdoor air. The overall effect of forests at night is that they
cool the air and release moisture, but they do not create dangerous CO2 pockets. In fact, the world's forests are critical carbon sinks—they absorb far more CO2 overall than they release.
So, if you enjoy sleeping with your window open to hear the trees rustle, you have nothing to worry about. The outdoor air is still far cleaner and richer in oxygen than indoor air in a sealed, plant-free room.
What about the smell of soil or dampness from plants at night?
This is a separate issue from CO2. Some potting soil can release a musty or earthy smell at night, especially if it stays damp. That smell is not dangerous, but if it bothers you, use a pot with drainage holes, water only when the top inch of soil is dry, and consider using a small dehumidifier or air purifier near your plant corner. A
small indoor air purifier with a carbon filter can remove any minor odors and also help with dust and pollen.
Find compact air purifiers for bedrooms on Amazon to keep the air fresh and clean.
Is there any way to reduce nighttime CO2 from plants even further?
If you absolutely want to minimize any possible CO2 release, you could:
- Place plants in a room with good ventilation (window or fan).
- Use a grow light to give them some artificial daylight hours, which can shift their respiration pattern.
- Choose CAM plants like succulents and cacti, which handle CO2 differently.
But honestly, for the vast majority of people, the standard houseplant is so low in CO2 output that no extra steps are needed. The benefits of having plants far outweigh any
