All about CO2

The rest

There’s always something about anything that simply cannot be categorized! The same is true for CO2 too.

This section provides answers to questions that are as equally interesting and useful as they are elsewhere in this compendium - it is just that we found it difficult to slot these into any section!

1. Why do plants breathe in CO2 while animals and humans breathe it out?

Plants are autotrophs - they can make their own food. In order to make this food, they need to absorb CO2 along with sunlight and water for photosynthesis, which makes sugar and food.

Humans and other animals are heterotrophs. They cannot make their own food and energy and instead they need to obtain these from outside - which they do from plants. These foods need to broken down into energy within their bodies, and for that we need oxygen which we breathe in. The food is broken down into energy and CO2, and this CO2 needs to be let out.

2. What happens when there is too much CO2 in the human body?

A condition of excess CO2 buildup in your body is termed Hypercapnia. This condition can result in headaches, dizziness, and fatigue, and in extreme cases, serious complications such as seizures or loss of consciousness.

Web resources:

An Overview of Hypercapnia - verywell health - Link

3. What will be the CO2 level in a closed room with limited ventilation?

Carbon dioxide concentrations indoors can vary from several hundred PPM to well over 1000 PPM in areas with many occupants present for an extended period of time.

The World Health Organization specifies a limit of 1000 PPM for closed spaces as healthy limit. Even at CO2 levels only slightly above this threshold, some occupants may have minor discomforts such as headaches, drowsiness, lack of concentration, fatigue etc. However, real health hazards from high CO2 concentrations will start at much higher levels of CO2 in the ambient air.

4. What atmospheric levels of CO2 will start affecting breathing?

Organizations such as OSHA have established a Permissible Exposure Limit (PEL) for CO2 of 5000 PPM (0.5% concentration) averaged over an 8-hour work day. Humans can start experiencing some difficulty in breathing at this level, especially if they are under this environment for several hours.

At even higher levels, CO2 can cause asphyxiation as it replaces oxygen in the blood. Exposure to concentrations above 50,000 PPM can be life threatening.

5. What is the concentration of CO2 in a human being's exhaled breath?

The gas exhaled by us contains 4-5% by volume of carbon dioxide, a hundred-fold more than the concentration in the air we inhale.

6. What happens if I add CO2 to milk?

Some folks think adding CO2 to milk could result in something really interesting to drink.

They will be disappointed.

Adding CO2 to milk changes the chemical environment of proteins in the milk, causing them to curdle and coagulate. The process becomes a chain reaction as you add more CO2 gas to the mixture.

You will be left with a product that is hardly drinkable, leave alone being tasty.