Is it dangerous to sleep with plants? Here’s what science says

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The belief that sleeping with plants is dangerous because they deprive us of oxygen or gas us with the carbon dioxide resulting from their respiration is widespread. Many people do not want to have plants in their bedroom to avoid competing against a living being considered a relentless monopolizer of the breathable air of the environment.

I am going to start this article by advancing the conclusions: no, sleeping with plants is not dangerous at all, they are not going to suffocate us while we sleep. On the contrary, the plants in our rooms can bring us numerous benefits, as we will see later. Like any myth, the one that portrays our houseplants as mere oxygen thieves has some truth to it. So let’s dissect this belief to understand how it was generated and separate fact from fiction.

Atmospheric composition engineers

To explore the origin of this myth, we need to know how plants manipulate the concentrations of gases in the air around us. They do this through two processes: photosynthesis and respiration.

In short, photosynthesis is the process by which the plant synthesizes oxygen and glucose from carbon dioxide, water, and sunlight. Consequently, it is a process that necessarily takes place during the day. The general chemical equation of photosynthesis is as follows:

6 CO2 + 6 H2O + Sunlight –> Glucose + 6 O2

In other words, the plant takes 6 molecules of carbon dioxide (CO2) from the air, which react with 6 molecules of water absorbed by the roots to produce, through the intervention of sunlight, a molecule of glucose and 6 molecules of oxygen (O2). Glucose is the source that plants use to obtain energy and perform various vital functions.

Respiration is the opposite process: the plant consumes oxygen and the glucose it has synthesized during the day, generating as a result energy, CO2, and water vapor. Thus, the general equation would be as follows:

Glucose + 6 O2 –> 6 CO2 + 6 H2O

Like us, plants breathe all day long, but during sunlight hours, respiration is masked by photosynthesis, which is the predominant process.

The exchange of gases (oxygen, CO2, water vapor, etc.) occurs through organs located in the epidermis of the “green” parts of the plant (such as leaves or green stems) called stomata. Lenticels, lenticular-shaped openings in the woody parts of plants, are also involved. Stomata consist of a hole flanked by two cells that function as gates, closing and opening the hole depending on various factors, such as water availability, atmospheric CO2 concentration or light intensity, among others. In contrast, lenticels are continuously open.

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Stomata (left image) and lenticels (right image) are structures through which gas exchange occurs between the plant and its environment. Rodrigo AF y Willow (Wikimedia Commons)

Once you have assimilated all this, it is also necessary to know the three types of plants that exist depending on how they integrate CO2 in photosynthesis:

  • C3 and C4: although they have some differences in the way they metabolize CO2, for this article it is sufficient to say that these two groups of plants capture CO2 during daylight hours to use it in the photosynthetic process that is occurring at that time. Therefore, they open their stomata during the day and close them at night to reduce water loss by evaporation. Most of the plants we know have one of these two metabolisms.

  • CAM: it is the abbreviation for “crassulacean acid metabolism”. As its name indicates, this metabolism is characteristic of crassulaceae and cacti, plant groups that live in very hot and dry places. These plants have a problem: if they open their stomata during the day to collect CO2, they would dry out, since water also escapes through the stomata in the form of vapor, and in a dry and hot place where water evaporation is more intense, this is not the most advisable thing to do. Therefore, these plants open their stomata at night, absorb atmospheric CO2 and store it until the next day for use in photosynthesis.

Oxygen thieves?

Based on this brief review of plant physiology, it seems that it is best to sleep with cacti and crassulaceae, since, at night, although they generate CO2 through their respiration, they also capture a large amount of it, so we are not in danger of suffocating. What about C3 and C4 plants? Is it advisable to have them around at night?

Let us remember that these plants close their stomata almost completely at night. However, their lenticels remain open. Even so, we should not worry at all. The first reason is quite obvious. Nobody sleeps in airtight rooms. On the contrary, they are usually ventilated to a greater or lesser extent, so that the air is constantly renewed. However, it would also be fine if we slept in an airtight room with C3 or C4 plants, since the oxygen they produce during the day far exceeds the oxygen they consume at night. There is no point of comparison.

If we think about it carefully, it doesn’t make much sense for plants to be able to deoxygenate a room either. If that was the case, a forest dominated by deciduous species, i.e. those that shed all their leaves during autumn, would be impassable at that time of the year and in winter. Without leaves, plants cannot photosynthesize and do not produce oxygen, but they do continue to breathe through their lenticels. The result would be an area with very low oxygen concentrations, which is not the case.

Ficus elastica robusta
A plant of the species Ficus elastica enclosed in a watertight compartment showed that the plants release derisory amounts of CO2 and consume very little oxygen at night. Mokkie (Wikimedia Commons)

The amount of oxygen consumed by the plants we usually have in our homes is, in general, derisory, although it varies depending on several factors, such as their size (the bigger they are, the more they consume), their growth rate or the environmental temperature, among others. In addition, the oxygen they produce through photosynthesis far exceeds the oxygen they consume throughout the night, guaranteeing us a more than sufficient oxygen reserve for the whole day.

Rather, it should be the opposite: it is the plants that should be afraid of sleeping with us, since we are homeothermic animals (“warm-blooded”) and, therefore, we consume disproportionately more O2 and release much more CO2 than any plant. For example, it is estimated that 5 kg of petunias consume 0.01 l for 8 hours at night. In contrast, an adult person consumes about 0.26 l of oxygen per minute, so in 8 hours he/she will have consumed 124.8 l. The difference is so abysmal that there is no plant large enough to fit in our room that can match the amount of oxygen consumed by a human being. The same can be said of our pets. Therefore, it is much worse to sleep with another person, our dog, or cat. Although, in reality, as we all know, nothing happens in these situations either: our rooms have enough oxygen for everyone.

Plants purify the air

It is clear then that sleeping with plants is not harmful to our health. Even better, having plants in our bedroom can bring us several health benefits. We have just seen that plants absorb much more CO2 than they produce during their respiration. Therefore, they are very useful to avoid an excess of this gas indoors. Moreover, plants can also enzymatically degrade other gases and volatile compounds harmful to our health, such as formaldehyde, benzene, nitrogen oxides, etc. In other words, plants help clean the air.

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Plants contribute to air purification. Leonardo AI

We have also seen that plants emit water vapor as a result of the chemical reactions that occur during respiration. The relative humidity of indoor spaces is important. In fact, low levels of this parameter are associated with eye, respiratory and skin problems. For this reason, if we want to have an adequate relative humidity in our rooms, nothing better than installing a few plants.

To sum up, sleeping with plants is not only not bad, but contributes to our well-being. The plants in our rooms are beneficial organisms for our health. The only danger they may pose is that we accidentally stumble upon a pot when we groggily go to the bathroom.

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