As a rule of thumb, whenever an alarm bell goes off, the party has to be prepared to face opponents. There is, for example, a scripted alarm in Level 4 of Wizardry: Proving Grounds of the Mad Overlord after the party has entered the Testing Ground Control Center.
However, "Alarm" is also the name of a chest trap in Wizardry I - V, although the trap is called "Sirens" in Wizardry V: Heart of the Maelstorm.
When the trap is triggered, new monsters appear, which may be extremely unfortunate after a hard fight to win the chest in the first place.
The trap may be found in almost any level of a maze as its amount of peril is connected to the strength of the monsters that roam the dungeon.
Note: The type (level) of treasure found in the chest is normally linked to the monsters that were fought just before opening the chest. When an alarm trap is triggered, however, the loot from the chest will match the treasure normally associated with the group of monsters fought after opening the chest.