fire tower

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A tower in which a lookout for fires is posted.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A watchtower to search for fires in a forest.
• noun In a high building, a stairway protected by several inches of concrete and entered through a kind of "air lock" that prevents the smoke to enter inside it.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a watchtower where a lookout is posted to watch for fires