Carbon dioxide in it's solid form (dry ice) is used in large scale refrigeration processes.
Carbon dioxide is used in fire extinguishers.
Carbon dioxide is used in medicine (it promotes exhalation).
Carbon dioxide is used in carbonated drinks.
Magnesium oxide is used as an animal feed supplement.
Magnesium oxide is used in antacids, cosmetics, toothpaste, and ointments.
Magnesium oxide is used as filler in rubber compounding.
Magnesium oxide is used in fertilizers.
Magnesium oxide is a basic ingredient in product formulations for the steel industry.