You will need
  • * 0.5 l of water;
  • * wide non-metal bowl;
  • * 2 tablets gidroperita;
  • * crystals of potassium permanganate;
  • * potassium (sodium) nitrate;
  • * spoon for heating.
The most affordable way is: put a bowl of water on the table and dissolve it in tablets gidroperita. To accelerate the process in advance they can be crushed.
Once gidroperit is completely dissolved, throw a few crystals of potassium permanganate, and stir. The liquid will hiss and begin to foam, these phenomena are accompanied by the secretion of oxygen.
Termination of hiss, accordingly, will mean the end of the reaction. To resume you have to add one component: the fluid is brown, add the peroxide, and if the color upon termination of the hiss has not changed - a couple of crystals of potassium permanganate.
Over a bowl, you can get some or just put her in her room and enjoy the easier breathing.
In order to get oxygen, you can also take potassium (sodium) nitrate (sold in shops for gardeners) and heat it in a spoon. In this case, the oxygen will be allocated in the heating process.