There are two main approaches to this problem:
1) Using the collision layer system.
Assign the area to a layer, and then set the other areas to ignore that layer in their layer mask.
See this page for an introduction to how collision layers work.
2) Using groups.
Put the area in an "ignore" group (use whatever name you like. Then in the other areas'
area_entered code, use
if area.is_in_group("ignore") to test for the group.
Option #1 is the preferred solution, because this way the engine isn't even testing collisions between those areas because they can't "see" each other and you don't need to write any code to make it work.