There are two main types of smoke alarm tech, says Raman Chagger, principal consultant at BRE, the Building Research Establishment. Ionisation-based systems use a tiny amount of radioactive material to charge, or ionise, particles in the air which flow between two small plates. Should smoke interrupt that flow of charged particles, the alarm goes off.
* @param {number[]} nums2 - 基准数组（nums1的元素都来自这里）
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Tan is far from the only person turning to Reddit, which launched in 2005 and was once viewed as a place for nerds.
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