To provide a gas mask and a dust mask which can correctly clock and integrate used time, and are safely and efficiently used.

The gas mask includes: an absorption can 2 for absorbing toxic gas; a surface body 3; a surface body switch 20 arranged in the face contact part 15 of the surface body 3, turned on by depression with a part of the face when a user wears the surface body 3, and turned off when the surface body 3 is removed from the face; a clocking means for clocking the wearing time of the surface body 3 interlocked with the surface body switch 20; a time setting means for setting the usage limit time of the absorption can; a storage means for storing data; an alarm means for issuing an alarm when receiving a signal; and a calculation control means for integrating the time clocked by the clocking means, and outputting the signal to the alarm means when the integrated time reaches the time set by the time setting means.