The NHL permits each team to carry up to 23 players on its active roster, subject to the constraints of the salary cap. However, it also requires a minimum of 2 goaltenders, 6 defenseman and 12 forwards on its active roster at all times. A player is not considered on the active roster if they have been placed on the Injured Reserve List or are suspended by the NHL.
If the team falls below any of these minimum categories, they are permitted to recall a player without subjection to waivers in order to meet the NHL minimum roster requirements. However, the player must be returned to the affiliate when the player he is replacing returns from their inactive status. Emergency recalls work generally the same way but does have some specific rules and allowed behavior. The specific language for this question of emergency recall is at the end. This is being provided for information because of some uncertainly with bloggers on how exactly this works. If you need a nap then read the following very carefully.
(j) A player who has been loaned to a club of any league affiliated with the NHL may be recalled at any time subject to the provisions of Articles 13.10(k)[next para] and 13.10(l)[ see the (1) Emergency Recall Below].
(k) During the period following noon of the twenty-sixth(26) day immediately preceding the final day of the regular season no player may be recalled from loan to a club of any league affiliated with the NHL, except that:
(i) A Club may exercise four recalls from a club or clubs of any league affiliated
with the NHL, of player(s) listed on its own Reserve List.
(ii) Players may be recalled under Article 13.10(l). (see the (1) Emergency Recall Below)
(iii) Players may be recalled upon completion of the regular season and playoff schedule of the club to which they were loaned.
(l) Emergency Recall.
(i) A player on loan to a Club of any league affiliated with the League may be recalled from such loan under emergency conditions at any time for the duration of the emergency only following which he must be returned promptly to the club from which he was recalled.
(ii) Emergency conditions shall be established when the playing strength of the loaning Club, by reason of incapacitating injury or illness or by League suspension to its players is reduced below the level of two (2) goalkeepers, six (6) defensemen and twelve (12) forwards. Proof of the existence of the emergency conditions including the incapacity shall be furnished to the Commissioner of the League upon request made by him.
(iii) For the purpose of establishing the existence of emergency conditions at any time, to support the recall of a player or goalkeeper for participation in any playoff game, it shall be deemed that the player(s) on loan following noon of the twenty-sixth (26th) day immediately preceding the last day of the regular season are continuing on loan for the remainder of the season notwithstanding that the loaned club(s) may have been eliminated from further play for the season.
13.11. Waiver Notification. Player(s) and the Association shall be notified immediately whenever a Player(s) clears or is claimed on waivers.
13.12. Transfer Form.
(a) Player(s) assigned to or from a minor league club shall receive a transfer form. In order to make said assignment effective the Club must, prior to that player playing in a game and in any event within 24 hours of assignment, send a copy to the NHLPA and NHL.
(b) (i) A Club recalling a Player from a minor league club, under emergency conditions, must specify on the transfer form the name of the injured, ill or suspended Player whom the Player on emergency recall is replacing.
(ii) When an emergency condition terminates, the Club must submit a transfer form indicating whether the Player's status has converted to regular recall or is assigned to his minor league club.