Example - for a 3-bedroom, 2,000-sq.ft. home, with an exhaust-only ventilation strategy, and a target ventilation rate of 50 CFM you would need to install a 50 CFM fan with an adjustable-speed DC motor for continuous operation.
Quick Answer. Trenches were built during World War I to protect stalemated troops on both sides from artillery and rifle fire. Although the war began with rapid movement of the German army, when the Allied forces stopped the Germans, both sides dug trenches to help avoid losing territory they had gained.
Life in the trenches of the First World War. Although most of us think primarily of the Great War in terms of life and death in the trenches, only a relatively small proportion of the army actually served there. The trenches were the front lines: the most dangerous places. But behind them was a mass of supply lines, training establishments, stores, workshops, headquarters and all the other elements of the 1914-1918 system of war, in which the majority of troops were employed.