When a Change is within its change window and is moved into the implementation phase, the CI for that change is automatically moved into maintenance. If any events related to these CI's are generated, the alert rules will not be processed for them.
However, you can also suppress all the alerts that come in during a maintenance window irrespective of the CI's being in maintenance mode
Event Management has some advance Script Includes that you can use to inject your own logic in between the Event processing and Alert creation (search for EvtMgmtCustom_*): Components installed with Event Management [Madrid]
In these Script includes, if you return false, the event will be marked as 'Processed' and ignored. In this way, incident creation can be stopped during maintenance windows.