If SN is less than 95% pure, doesnot death occur?

[vehbii]

Hello, I am writing with translate because I am not good at forming sentences in English. I apologize for my spelling mistakes. My question is this: I live in Turkey and I don't think I can do the SN test because of the difficulty of the English texts and the difficulty in finding materials. Should I trust the sellers selling SN on the internet here? Many of them have stated that the purity is over 98%, is this true? If the SN is less than 95% pure, won't death occur? If not, what will happen? Thanks in advance for your answers