When it comes to helmets coming off on the field, there are a lot of new things to think about this year.
1. When the ballcarrier's helmet comes off, the play is immediately dead.
2. If ANY player's helmet comes off during a play and the helmet did not come off as a result of a penalty by the other team, that player has to come out of the game for one play. He cannot be "bought back in" with a time-out and it doesn't matter if it was the last play of the second half.
3. Once a player's helmet comes off in the field of play, he is by definition OUT OF THE PLAY. As a result, if any player hits him, it is a 15-yard penalty against the player who hits the helmetless player.
4. Once a player's helmet comes off in the field of play, he cannot continue to participate in the play outside of the immediately action in which he was engaged. In other words, he can finish making a tackle or pick up a ball in his immediately vicinity, but he cannot take several steps to make a tackle, block, or otherwise participate in the play. If he does, it is a 15-yard penalty on the helmetless player.