; (C) provide real-time information regarding methane, oxygen, and carbon monoxide levels, and airflow direction, as appropriate, with sensing, annunciating, and recording capabilities; and (D) can, to the maximum extent practicable, withstand explosions and fires. (2) Content of regulations The Secretary shall evaluate and, as appropriate, require— (A) the installation of atmospheric monitoring and recording devices on mining equipment; (B) the implementation of redundant systems, such as the bundle tubing system, that can continuously monitor the mine atmosphere following incidents such as fires, explosions, entrapments, and inundations; and (C) the implementation of other technologies available to conduct continuous atmospheric monitoring. . 504. Study on respirable dust standards Section 202 of the Federal Mine Safety and Health Act of 1977 ( 30 U.S.C. 842 ) is amended by adding at the end the following: (i) Reports (1) Study Beginning August 1, 2021, the Secretary of Labor shall undertake a retrospective study that evaluates the effectiveness of the Department of Labor’s final rule entitled Lowering Miners’ Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust Monitors (published May 1, 2014; 79 Fed. Reg. 24813), the data regarding the use of continuous personal dust monitors (in this paragraph referred to as CPDM ), and the rising number of cases of progressive massive fibrosis (PMF) to determine whether— (A) the 1.5 mg/m 3 respirable dust standard that was included in the final rule should be further lowered to better protect miners’ health; (B) the 100 µg/m 3 standard for quartz (crystalline silica) in respirable dust should be lowered to better protect better protect miners’ health; (C) the frequency of CPDM sampling should be increased; (D) engineering controls and work practices used by mine operators to achieve and maintain the required respirable coal mine dust levels should be modified