Ventilation of hydraulic and transportation tunnels is complicated by a large cross-section of underground excavations, their considerable length and a large volume of blasting operations. Due to low air velocities in such excavations, the most common forcing method of ventilation does not provide rapid removal of harmful gases after blasting. Exhaust ventilation is also ineffective, as a large volume of slow-moving air is formed in the face area. ...

In the mining industry, especially during the construction of hydraulic engineering structures, workings with a cross-section of 50–80 m² are driven over considerable lengths. To ventilate such workings, a large volume of fresh air must be supplied to the face through ventilation pipes. Sometimes this is practically difficult to achieve, since ventilation pipes have high resistance and allow significant leaks.