When a gas gets exposure to electricity or heat or any energy source; the ions, radicals, free electrons and other molecular portions in it get mixed and start collision with each other. And, this happens to give a Plasma treatment that results in the removal of all kind of organic contamination.
That is why people warm the cold food in microwave and then eat it. This is a mere example of treating by plasma but this technique has major applications in medical field. Skin tightening, donating of plasma for some medical treatment and much more are used of treating through plasma.