• Question: Why is c02 deadly?

    Asked by to Amelia, Izzy, Sarah on 20 Mar 2014. This question was also asked by .
    • Photo: Isabel Webb

      Isabel Webb answered on 20 Mar 2014:

      CO2 (carbon dioxide) is not deadly – it is the lack of oxygen that is deadly.

      CO2 is essential for plants to grow. They need it to do photosynthesis, a reaction that uses the sunlight to make sugars for food. Oxygen is a waste product of this reaction.

      CO2 is also a waste product, made by respiration – which is the process of converting food into energy for growth or movement. This needs oxygen. If there is no oxygen, we (or plants) can’t respire and can’t survive. Since plants can use CO2 and turn it into oxygen, it is unlikely that they will be killed if you put them in CO2.
      Humans and animals, however, can’t make oxygen. If they are in a room of air, with no new air coming in, they will use up all the oxygen, turning it into carbon dioxide, and so will die.
      Our bodies have evolved to recognise high levels of CO2 rather than low levels of oxygen – so when you have to breathe heavy its because your body senses high CO2 and so assumes you need more oxygen.

      CO, carbon monoxide, is deadly however. It binds ‘haemoglobin’ which is the chemical that carries oxygen around the body. So, if you breathe in too much CO, it is definitely deadly.

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