This video shows why you cant always trust all information on the internet, as well as shows the basics of torque wrenches and a few oddball calculations you might run across when building custom things.
Underground mine ventilation. Underground mine ventilation provides a flow of air to the underground workings of a mine of sufficient volume to dilute and remove dust and noxious gases (typically NOx, SO2, methane, CO2 and CO) and to regulate temperature.
Tunnel ventilation is a special, yet simple summertime ventilation system. Its goal is to provide air velocity and air exchange concurrently in a barn. Fans (called tunnel fans) are placed in one gable endwall of a building (see Figure 1).