11 is high. Ask your landlord to install mitigation system right now.
N*s
10 楼
unless you can prove your health is damaged by radon, which is unlikely at least I wish not, you don't want to feed the lawyer. Do ask landlord to install mitigation system.
unless the house was sold within the past 5 years or so, it is unlikely owner would test the radon level. So I guess many people currently live in a house with basement >4 radon level and not know it.