How to solve the problem of return air at the new level of mine and the level of preparation?

Article 112 The total return air lane or the main return air lane must be introduced when the mine develops to a new level and the return air prepared for the new mining area. Before the ventilation system is formed, this return air can be introduced into the intake air at the production level; However, in the mine with gas emission or coal (rock) and gas (carbon dioxide) outburst danger, when opening up a new level and preparing a new mining area, it is necessary to excavate in the coal (rock) layer without gas emission or coal (rock) and gas (carbon dioxide) outburst danger first, and form a ventilation system. In order to form the return air of driving roadway, the intake air can be introduced at the production level. The concentrations of gas and carbon dioxide in the above two kinds of return air shall not exceed 0.5%, and the concentrations of other harmful gases must conform to the provisions of Article 100 of this regulation, and safety measures shall be formulated and reported to the technical director of the enterprise for approval.