Hans Karman has contributed to Australian Philately at local, state, national and international levels.

His service as Exchange Superintendent of the Philatelic Society of Canberra, and as a member of the Society's Council, for a period of over twenty years represent an outstanding contribution to local philately. His skills in the role were outstanding and soon after his appointment Hans prepared a computer program to handle the exchange branch circulation and its accounts. He pioneered the sending of a selection of books to several smaller stamp clubs in southern NSW, a service that continues today.

Hans Karman was elected to the ACT Philatelic Council in 1984 and immediately assumed the post as Treasurer which he held until 1992. Besides his work as Treasurer, he playing lead roles in two major APF Projects and contributed to State judging and exhibiting courses. His contributions to the courses have specifically concerned presentation, mounting of exhibits and postal history.

He has been actively involved with Canberra Stampshows including the 2002, 2004 and 2006 modified National Exhibitions and was Treasurer of Austamp 90, a full national exhibition. Hans Karman became a National judge in 1997 being qualified to judge postal history, social and postal stationery.

Hans Karman has been an active philatelic exhibitor, researcher and writer. He has exhibited nationally and internationally with his major exhibit Free Mail of Australia - States and Commonwealth attaining Gold medals at international exhibitions, each time with a completely redesigned exhibit. He also exhibited in Social Philately, Postal Stationery and, more recently, Postcards.