Describe the role of heroes in film Noir

Film noir features many different types of characters however some styles of characters are more common than others, these are the characters you are most likely to encounter whilst watching a film noir. Heroes (or anti-heroes), corrupt characters and villains included down-and-out, conflicted hard-boiled detectives or private eyes, cops, gangsters, government agents, a lone wolf, socio-paths or killers, crooks, war veterans, politicians, petty criminals, murderers, or just plain Joes. These protagonists were often morally-ambiguous low-life from the dark and gloomy underworld of violent crime and corruption. Distinctively, they were cynical, tarnished, obsessive (sexual or otherwise), brooding, menacing, sinister, sardonic, disillusioned, frightened and insecure loners (usually men), struggling to survive - and in the end, ultimately losing.
Film noir will always have a hero because it gives the film strength and a character to attach to. A hero will often be flawed or corrupted in some way or another to make his journey more difficult and show character building. Noir heroes are often alienated or isolated making them seem more rugged and independent. Heroes in Film noir are constantly smoking this connotes their one comfort or security. Their cigarettes are the only certainty they have. The heroes will often have a run in or romantic affair with the femme fatale character, the idea behind this is create a deeper plot line and link sequential stories together to make a more interesting plot line.