Egg smellers?

[klf73]

Ok, I have read some people smell their eggs to see if they are any good. I have a poopy egg that smells a little different. I'm not sure if it is the blood that a chick with a rough naval got on it or if it is just bad. I am on day 16 minimum (not sure of date laid). any ideas? I tried candling but I'm just not sure, I can't see much, it looks full, but what would a rotten one look like?
Krista

 

[Frizzledhen]

Rotten eggs SMELL, no guessing about it. If the egg is dark except at the top where the air cell is, I would leave it under the broody or in the incubator for a few more days.