Learn English – What’s the difference between “take out”, “take from” and “take out from”

Basically, no, there is no difference in this case. The only real difference here is that "walk out" specifies method of travel (walking). But you already knew that.

I would caution you, however, that there are many contexts in which there is a difference. The phrase "get out", especially when used as an imperative (command), quite often implies a very harsh tone, anger, and even a threat. However, because you are using it in a context that merely discusses the act hypothetically, it won't be taken as harsh.

Another caution: this is a somewhat less common way to use "get out", and a less common way to say what the sentence is trying to say (at least in my experience). It sounds somewhat out of place there. A better phrasing would perhaps be one of the following:

• The moment you leave the building...
• The moment you exit the building...
• The moment you arrive outside (of the building)...

When a verb has no object, we call it intransitive:

Shoes wear out.

When a verb takes an object, we call it transitive:

Running on concrete wore out his knees.

"His knees" is the object. "Running on concrete" is the subject.

We can "flip" a transitive verb in the active voice (see the sentence about "knees" above) and make it a passive construction:

His knees were worn out by running on concrete.

We can omit the agent (that which performs the action):

His knees were worn out.

Something wore his knees out, but we don't know what it was. Was he a fireman who climbed ladders all day? In this form, we're basically saying his knees are in certain state or condition, since the agent is unexpressed.