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.
Ocean trenches have relatively steep sides falling to the ocean floor. Ocean trenches are typically caused when an oceanic crustal plate slides under a lighter continental plate or another oceanic plate. It is believed to work by density.Where one plate slides under another, this is called subduction.t least five trenches are over 6 miles (10 km) deep. The greatest ocean depth to be sounded is in the Challenger Deep of the Mariana Trench, at a depth of 11,034 m (36,201 ft) below sea level.