Except as provided in subsection (b) of this section: an individual who otherwise is eligible to receive benefits is disqualified from receiving benefits for each week for which the Secretary finds that unemployment results from a stoppage of work, other than a lockout, that exists because of a labor dispute at the premises where the individual last was employed; and if separate branches of work that usually are conducted as separate businesses in separate premises are conducted in separate departments on the same premises, each department shall be considered a separate premises for the purposes of this subsection. A disqualification under this section does not apply to an individual who satisfies the Secretary that the individual: is not participating in, financing, or directly interested in the labor dispute that caused the stoppage of work; and does not belong to a class or grade of workers that, immediately before the stoppage, had any members: employed at the premises; and participating in, financing, or directly interested in the labor dispute.