An apparatus includes a C-shaped susceptor including a first substrate placement portion capable of placing the substrate, and an opening portion, a substrate stage including a second substrate placement portion capable of placing the substrate, and a susceptor support portion configured to support the susceptor, and a complementary portion formed separately from the susceptor support portion, engaged with the susceptor support portion, and configured to complement an opening portion of the susceptor to form the susceptor into an annular shape in a state in which the susceptor support portion supports the susceptor. When the substrate is placed on the second substrate placement portion and the second substrate placement portion is located at a predetermined distant position with respect to the heat radiation surface, the susceptor forms the annular shape together with the complementary portion to surround the substrate.

A smoke alarm has a housing with a heating device for heating walls of the housing to a temperature above the dew point. The heating device has at least one heating light emitting diode (LED). The heating LED has an opening angle for the emission of light, which opening angle leads to an irradiated area of the housing.

A thermal radiation element includes a substrate; and a plasmonic perfect absorber in which a first conductor layer covering one main surface of the substrate, an insulator layer, and a second conductor layer are laminated in this order, in which the first conductor layer is provided with electrodes through which a current flows in an in-plane direction of a main surface of the first conductor layer.