PURPOSE: To prevent the inner surface of the shielding plate from clouding due to expiration of a user by designing a full-face type helmet so that the breathing space inside the jaw guard part may be wide. In addition, the wide breathing space is designed so as to be filled with air and so as to be prevented from invasion of smoke, etc., when air is supplied from an air tank to the breathing space in case of emergencies such as a fire in a car vehicle.

CONSTITUTION: In the objective helmet, the front wall 4 of the jaw guard part 1a of the helmet body 1 is composed of an upper half unit 4a inclined downward and forward and extending from the upper edge of the jaw guard part 1a to the top part 4t and a lower half unit 4b extending from the top part 4t to the lower edge of the jaw guard part 1a. The upper half unit 4a is designed so as to widen the breathing space 8 inside the jaw guard part 1a and the lower half unit 4b is designed so as to narrow the lower part of the breathing space 8 between the lower half unit 4b and the jaws of a user (U). The jaw guard part 1a is equipped with an air-inlet 9 for supplying air from an air tank into the breathing space 8 in case of an emergency.