The first intermission takes place between the first period and second period.
The second intermission takes place between the second and third period.
The third intermission takes place before overtime periods, if the score is tied at the end of regulation. The intermission before overtime only lasts one minute in the NHL.
The fourth intermission takes place before the shootout if the score is tied at the end of overtime.
Intermissions last fifteen and a half minutes (seventeen for televised games) in the NHL and time is recorded by the game timekeeper and presented to fans on the scoreboard.
During intermission, players leave the ice through an opening in the boards to the locker rooms. Intermissions allow players to regroup and make adjustments to their game plan prior to the next period. During this time, the zamboni will also come onto the ice to perform necessary maintenance.
There are two intermissions in a regulation hockey game. The first intermission is between the first period and second period. The second intermission is between the second and third periods. There can be more intermissions if the game goes into overtime and shootouts.
In the NHL, intermissions between periods last fifteen and a half minutes. For televised games, the intermission will last 17 minutes. The intermission before the start of overtime lasts one minute.
Players and coaches go to the locker rooms to strategize for the next period. There is also a halftime show to keep fans entertained. This intermission period is also when the Zamboni comes out to do maintenance on the ice. You can watch an analysis and breakdown of the previous period by sports analysts on major television networks.