| 摘要 |
PURPOSE:To obtain such a structure that no dust sticks on an optical element by providing a smoke detection part which has the optical element and a smoke chamber coupled together through a replaceable transparent filter. CONSTITUTION:An inner cylinder 7 and an outer cylinder 6 are provided in the smoke detection part to form the smoke chamber, and optical elements 8 and 9 are fitted at its both sides. An opening part 7a is provided under the outer cylinder 6 and an opening part 6a is provided over the inner cylinder 7 to prevent disturbing light from entering the outer cylinder 6. Then, the thickness of smoke entering the inner cylinder 7 is detected by the light emitting element 8 and photodetecting element 9 fitted at the both sides through a transparent filter 10. |
