Vehicle seat with a side airbag device

A safety device for an automotive vehicle, comprising:

• a vehicle seat having a backrest extending in a transverse direction of the vehicle, the backrest having at least one lateral region and an upper region, and a headrest extending from the upper region;
• a side airbag device arranged in the backrest and having:
• an inflator;
• and
• a side airbag including a thorax section enclosing a thorax chamber in fluid communication with the inflator, and a head section separate from the thorax section and enclosing a head chamber, the thorax section and the head section each arranged in or on the backrest and each having an inner wall that forms an impact surface, and an outer wall, the head section configured to emerge from the upper region of the backrest beside the headrest upon actuation of the inflator, the inner wall of the head section configured to be offset in a transverse direction of the vehicle relative to the inner wall of the thorax section upon complete expansion of the airbag, and the inner wall of the thorax section and the outer wall of the head section each having an overflow opening, the overflow openings being in fluid communication and configured to allow a gas overflow from the thorax chamber into the head chamber;
• and
• a safety belt having an applied state configured to extend through a gap between the head section and the thorax section of the side airbag after inflation of the airbag.