Abstract: A safety device for a power chain saw or the like. The safety device has a mass body which is responsive to acceleration forces and is operatively connected with a brake device. The mass body has at least one support part under a holding force, the mass body being displaceable from a rest position under the effect of the acceleration force (a "monostable inertia switch"). The mass body in a preferred embodiment is made as a bar or rod magnetically attracted to a supporting surface and capable of being tilted from an upright or vertical position temporarily into electrically conducting engagement with an annular ring spaced therefrom and surrounding the upper free end of the bar or rod, permitting electrical connection to be established to actuate a brake device for stopping the power chain saw in case of an emergency, including tripping, falling, slipping, or sudden shock, as a safety feature of an operator of the power chain saw.