Pro: Survival

• Breathing provides the oxygen your body needs to function. It also removes wastes from your body. The average person can survive as long as 10 days without water, depending on the temperature, and four to six weeks without food. You can only survive four to five minutes without oxygen, at which point your heart stops beating, your brain cells die and your body shuts down.
  
  

Con: Environmental Pollutants and Toxins

• Breathing gives you much-needed oxygen, but it also introduces pollutants, toxins and other airborne threats to your body. While you do have some control over the quality of your air -- you could filter your home air or move to an area with fewer pollutants -- you cannot eliminate all potential irritants from the air.
  
  

Pro: Breathing is Partially Voluntary

• We can control our breathing to a point. This means, if you are in a circumstance where you know that you should not breathe, such as under water, you can hold your breath as a protective measure. You can also control your rate of breathing and how deeply you breathe. For example, when under stress, you can take slower and deeper breaths to calm down.
  
  

Pro and Con: Breathing is Mostly Involuntary

• We can control our breathing to a point and then our bodies take over. If you hold your breath longer past a certain point, you will pass out and start breathing automatically. In a dangerous environment, such as with a gas leak, this will force you to inhale something potentially lethal. At the same time, this automatic response ensures that you continue breathing, even when you are unconscious or sleeping. If breathing were not automatic, you would suffocate when you stopped consciously trying to breathe.