Don’t worry about an egg going bad and you not knowing it. Believe me; in this case theNOSE KNOWS. Rotten eggs smell awful. They won’t be able to sneak up on you. The gas hydrogen sulfide develops as bacteria breaks down the proteins in the egg white, creating that nasty gas smell. There’s another way to tell if your egg has gone bad. As oxygen gets into the egg, it creates an air bubble inside in place of moisture and carbon dioxide. This will cause the egg to float when placed in cold water (at least double the depth as the length of the egg). Anything other than a floating egg is fine to ingest. Don’t be put off by the other things that you might see in your egg. Some things may look odd to you, but don't worry, there is nothing wrong with your egg when you see the little red spots in the yolk. Those spots (usually referred to as meat spots) just mean that a blood vessel ruptured during the formation of the egg. They are diluted as the egg gets older, which means that if you actually see them, your eggs are still quite fresh. Another misinterpreted egg issue is when you see a white strand (chalazae) in the egg white, usually right next to the yolk. It reminds me of a white umbilical cord. They are only there to keep the egg yolk centered and are sometimes more obvious in some eggs than others. Even if you see an egg white that is cloudy or has a yellow or green hue to it, it doesn’t mean that it’s bad. In fact, quite the opposite because it indicates that the carbon dioxide just hasn’t had enough time to escape the egg. Even if you end up with a fertilized egg, it’s still safe to eat.
Read more at http://www.preparednesspro.com/safely-preserving-eggs#0oCqg3rCsg6yVeku.99