Normally :40 during the course of the game, but :25 for either offensive or defensive helmet if there is a 10-sec runoff option. Reference last year's CFO 10-Second Runoff: Play Situations document:
"12. During the play, B77 loses his helmet. The ball carrier is tackled inbounds short of the line to gain.
RULING: B77 must leave the game for one play and Team A has the option of a 10- second runoff. Team B may avoid the runoff and/or keep B77 in the game by being granted a team timeout; note that the single timeout accomplishes both. Play clock: 25 seconds. Game clock starts on the referee’s signal if there is a 10-second runoff and on the snap if there is no runoff."
