MSHA is required to inspect each underground mine four times a year and each surface mine twice a year for health and safety compliance. Certain mines with high levels of explosive or toxic gasses are inspected more often. Inspections are also conducted in response to complaints of hazardous conditions.
MSHA inspectors work out of district offices for coal mines and metal and nonmetal mines located across the country. On finding any violation of a health or safety standard, an inspector will write a citation that specifies the standard violated and evaluates the gravity of the violation by several factors, including likelihood of injury. An inspector may determine that the violation was “significant and substantial” - or reasonably likely to result in a serious injury or illness nature - or that it was caused by the operator's unwarrantable failure to comply with the standard. These carry additional penalties and could result in an order of withdrawal.
An inspector may also issue an order to withdraw due to imminent danger, failure to correct a violation within the appropriate time period, inadequate training of miners, or an unwarrantable failure to comply.
An inspection ends with a close-out conference in which the inspector explains the results to the mine operator. If desired, the operator may request a safety and health conference at the district level within 10 days, briefly explaining in writing why each citation or order should be conferenced.
In April 2010, MSHA began a special enforcement initiative, targeting mines that have poor compliance histories with “impact inspections”. These inspections are conducted at off-hours and days and may involve a large number of inspectors. Results of impact inspections are released in monthly news releases.