谢谢。
我刚查了查,这种不装风扇的叫 passive sub-slab suction。The passive method is commonly used in newly constructed homes, where deposited radon level is expected to be low. 最多只能减少50%的氡气。而装风扇的能减少99%。
It is very good and quiet. The radon level drop to around 15 from 400. However I bought all installation stuff and radon detectors from www.radondetect.ca