DECODE statement

Hi,

anyone know what I have done wrong in the following code? I get an error saying missing right parenthesis but I dont think this is the case. Am I using decode wrongly? I get same error if I replace it with IFF instead

select "T_EXPOSURE"."VALUE" as "VALUE",

DECODE("T_EXPOSURETYPE".description='DeltaVal',
DECODE("T_EXPOSURE".Value>=0,"T_EXPOSURE".Value,0),0) AS DeltaValLong
 from	 "T_EXPOSURETYPE" "T_EXPOSURETYPE",
	 "T_EXPOSURE" "T_EXPOSURE"