Abstract: More and more architectural designs set the fire vestibule together with the lobby on the first floor to form an enlarged vestibule. The increase of floorage，personnel gathering and presence of combustibles puts forward higher requirements for smoke prevention safety of the enlarged vestibule on the first floor. This paper analyzes the structural characteristics and smoke prevention requirements of the enlarged vestibule on the first floor, and puts forward the way of enhanced smoke prevention.

Key words: enlarged vestibule on the first floor of building, mechanical smoke prevention, natural smoke exhaust, enhanced smoke prevention