The 71-year-old of Greenland Close was last seen on Tuesday (January 28) at 8.25am by his partner.
He did not indicate what he planned to do but he is known to enjoy country walks, particularly around Cissbury Ring, north of Worthing.
Mr Scammel suffers from Bipolar disorder and has no medication with him. He is described as 5’ 3”, of slight build with dark brown hair and he has a moustache.
He is believed to be wearing a wax jacket, black jogging bottoms, a maroon sweater, green wellington boots and carrying a green rucksack.
PC Mark Newton said: “We are concerned for Mr Scammel and if anyone has seen him or knows of his whereabouts, can they call police on 101 quoting serial 1465 of 28/1.”