What is the meaning of “significant and substantial”?

Under the case law decided by the Federal Mine Safety and Health Review Commission, four elements must be proven to establish a "significant and substantial" (S & S) violation:

  1. The underlying violation of a mandatory standard;
  2. The existence of a discrete safety hazard contributed to by the violation;
  3. A reasonable likelihood that the hazard contributed to will result in an injury; and
  4. A reasonable likelihood that the injury in question will be of a reasonably serious nature.

Secretary of Labor v. Mathies Coal Company, 6 FMSHRC 1 (January 1984).