S Your new gas furnace may have been installed in one of two. ways, as a direct-vent (2-pipe-Fig. 2) application or as a. non-direct vent (1-pipe-Fig. 3) application. S In a direct-vent (2-pipe) application,your furnace uses air. from outside the home for combustion and ventsflue gas to the. outdoors.
For the biological concept, see Anti-predator adaptation. A defence mechanism is an unconscious psychological mechanism that reduces anxiety arising from unacceptable or potentially harmful stimuli. Sigmund Freud was one of the first proponents of this construct.
Iron Curtain (countermeasure) Iron Curtain is an active protection system (APS) designed by Artis, an American technology development and manufacturing firm headquartered in Herndon, Virginia. The system is designed to protect military vehicles and other assets by intercepting threats such as rocket-propelled grenades and rendering them inert.