I had a multi-fuel burner installed. When my chimney was swept the sweep advised that the liner should be 904 grade. The Installer also said 904 grade, yet when I researched I found 316 grade was suitable for domestic properties and is much cheaper. The sweep said the 316 would only last about 2 year before corroding and/or burning out. If this is the case, why are 316 liners allowed?