from NHLOfficials.com,

Each team has a freezer in their dressing room where they keep at least 80 game pucks at a temperature of 14F (-10C) the day before each home game. This will ensure the pucks delivered to the supervisor of the off-ice officials are frozen and ready for game use. Before the start of the game, fifteen pucks are taken from the home team’s freezer in a hard plastic cooler directly to the penalty box freezer. At the start of the second and third period, an additional fifteen pucks are taken again from the team dressing room’s freezer to the penalty box freezer, each time carried in a hard plastic cooler in order to keep them as cold as possible.

Also, in an effort to provide the players with the best possible puck each and every shift, the puck is changed for a new frozen puck every time a puck has been used for more than two minutes of actual playing time. This is done in order to bring consistency to every shift for the players on how the puck will react....

Frozen pucks helps the linesmen making great and fair face-offs as the puck, when dropped flat on the ice, will generally not bounce. The only downside of this procedure for all on-ice officials is that, when hit by an errant puck, well let’s just say that it create a bigger bruise as a frozen puck is much harder than a warm one!!!

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