This paper introduces a novel new smoke detector characterized by its very small size and very high sensitivity. The new detector is fundamentally based on an -particle radiation source like the well-known -particle smoke detector. However, instead of utilizing the principle of ionization of the air, the particles are made to strike the gate of an n-channel mosfet. This results in a net positive charge on the gate of the transistor. The current through the mosfet will be proportional to the charge on the gate and, hence, to the intensity of the particles. If particles of smoke enter the detector and screen the particles, the positive charge on the gate drops, which leads to a reduced current or total cut-off of the mosfet.