E jiri ya tụnyere ADC nke a na-emebu, onye na-afụ ụfụfụ nwere uru nke ire ere zuru oke, obere ihe fọdụrụnụ nke onye na-afụ ụfụfụ, na nnukwu mmepụta gas dị irè.Ọnụ ego mgbakwunye: ihe dị ka 1-3%, a pụkwara ikpebi ọnụọgụ ụfụfụ dịka njupụta nke ụfụfụ, nke nwere ike ịbawanye ma ọ bụ belata n'ụzọ kwesịrị ekwesị.