From the collective bargaining agreement.
SECTION 3. INVOLUNTARY OVERTIME
Junior, qualified, available, on-shift employee(s) will be required to work involuntary overtime. The Company will make every effort to give the employee as much notice as reasonably possible of the involuntary overtime. Additionally, no employee will be required to work involuntarily more than fourteen (14) consecutive days.
When Management has at least ninety (90) minutes’ notice that a shift is going to be extended, it shall notify employees required to remain beyond their scheduled shift at least thirty (30) minutes prior to the end of the employees’ shift. The Company will provide access to a phone in the event of a required extension.
Also
SECTION 6. IMMINENT DANGER
No employee shall be compelled to perform work or operate equipment that poses an imminent danger to life or serious physical harm to himself/herself.
So it's sort of open ended...