Why can a breach of the tightness of the chest cavity lead to suffocation?

The fact that our chest is completely airtight helps us breathe in and out on a daily basis, easily and without thinking about it. During inhalation, the pressure in the chest cavity becomes low, negative, compared to the pressure in the environment. Therefore, the lungs expand and air is sucked into them. If the chest is injured, then its tightness is broken. The lungs cannot expand. Pneumothorax may develop – air enters the chest and accumulates there. Therefore, the pressure in the chest cavity will be the same as in the environment. This will lead to the person being unable to breathe and may die from suffocation without medical attention.