Schell began officiating matches outside of Hungary in 1973, and was chosen by the International Ice Hockey Federation (IIHF) to make his debut at the Ice Hockey World Championships in 1977. In a six-year span from 1977 to 1982, he was one of the busiest IIHF linesmen, officiating 41 games in the top division of the Ice Hockey World Championships. In 1977, he set an unofficial IIHF record of 22 World Championships matches in a year, when he officiated 11 games at the A-division of the 1977 World Ice Hockey Championships in Vienna, and then another 11 games at the B-division in Tokyo. He was later assigned to another 30 World Championships matches combined at the 1978 World Ice Hockey Championships in Prague, the 1979 World Ice Hockey Championships in Moscow and the 1982 Ice Hockey World Championships in Helsinki. He also officiated the final games in 1978 and 1982.