They want to improve the flavor and crusty texture of the meat by maximizing the broiling and minimizing the roasting aspect of cooking. Pure broiling incorporates only radiant thermal heat, while roasting encompasses radiant, conduction, and convection thermal heats. With the door open, the pan and air inside the broiling unit do not become as hot as they normally would. This cooler temperature reduces the effects of conduction and convection cooking in the broiler. It does not reduce the intensity of the radiant heat emanating directly from the broiling element. Professional cooks use this open-door technique more than do home cooks because they tend to have a better exhaust systems.
** Asian Recipes