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.
Медведев вышел в финал турнира в Дубае17:59，详情可参考爱思助手下载最新版本
。业内人士推荐同城约会作为进阶阅读
（新华社北京2月25日电 记者朱基钗、胡浩、丁小溪、高蕾、胡梦雪）
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