Rule 450 – Offsides
Note 3: An intentional offside is made for the purpose of causing a stoppage of play regardless of the reason.
If some one does it on purpose its intentional, eg a clear on the goalie while attacking players are in the attacking zone.
A person receiving a puck who skates in beore the puck cross or receives a pass by accident or misjudgment should not be an intentional offside because the player was not intentionally trying to stop the play, In that situation he has screwed up an opportunity for himself so is not intentional.
From the case book on rule 451 – Delayed Offside Proedure.
2. If there is a hard shot at or in the vicinity of the goalkeeper, the intentional offside rule shall apply
3. When an attacking player comes out of the end zone and deliberately plays the puck, or checks a defending player bringing the puck out, it shall be classified as an intentional offside.
Hope that clears it up a little bit