Many moons ago I watched some 'expert' on TV, demonstrate how they blow air from their lungs into/onto the contents of a jar they had opened and were then quickly closing the lid on to but back in the fridge. The reason they said was if you do that you are briefly blowing away the oxygen in the jar and replacing it with carbon dioxide. This would then slow down the rate of spoilage. Does anyone do this? I admit I did do it for a week of so but it then occurred that maybe the carbon dioxide coming out of my lungs might contain some viruses etc. Is this so?