What constitutes an enclosed area for purposes of compliance with Table 1?

Some of the entries on Table 1, as well as paragraph (c)(2)(i), include specific requirements for tasks performed “indoors or in enclosed areas.” This term refers to any areas where, without the assistance of forced ventilation, the dispersal of airborne dust can be impeded and concentrations can build up. For example, a work area with only a roof that does not affect the dispersal of dust would not be considered enclosed; however, an open-top structure with three walls and limited air movement could be considered enclosed. Parking garages, pits, trenches, and empty swimming pools may qualify as enclosed areas.