???? ??? ????? ?? GB / T 18993-2003 ?????? ?????? ?????? ?????????? ?????? ???? ???????? ?????? ??????? ????? ???????? ?????? ???????? ???????? ?????? ?????? ????? ?????? ???????? ?????? ??????? ???????? (???? ????? ???? ??? ???? ??????? ????????) ?? ????? ?????? ??????? ??????? (PVC-C) ????? ??? ??????.
????? ??? ????? ?? ??????? 1 ? 2 ??? ????? ?????? ?????? ??????? ???????? ????????.
????? ???????: