A very important question — and the answer depends on a combination of the physics of blast waves, the structure of the building, and the degree of shielding and barriers along the way.
Let’s analyze it step by step.

🎇 What is a blast wave?

When a missile (or bomb) explodes, it creates a blast wave — a wave of fast, powerful air pressure that spreads out from the point where the explosion occurred.

This wave:

moves at supersonic speed (hundreds to thousands of meters per second), can partially go around obstacles, and weakens as it advances and encounters walls, corners, or other absorbing elements. 🏢 A description of the path in your building:

Entrance → left → 10 steps down → right → right → another 10 steps → left → shelter.

This is a winding, indirect path that includes several sharp turns and stairs.

From a physics standpoint: every turn (especially a 90° turn) disperses part of the energy of the blast wave. Stairs also break up the wave — because the wave spreads in a horizontal front, and the descent draws some of its energy up and down. Two right turns and one left turn make it very difficult for a blast wave to pass directly. ⚠️ Can the wave “travel” the whole way?

The blast wave can enter the building entrance —
but the more turns, stairs, walls, and opposing pressures there are (such as trapped air), the smaller the chance that the blast wave will reach the shelter with dangerous force.

In practice: it is almost impossible for a strong blast wave to reach the shelter with lethal force through such a route. It may be that a slight rumble or noticeable pressure would reach it, but not destructive devastation. If the shelter door is closed (as it should be), that blocks much more still. 🧪 Research and real-world experience: shelters built according to Israeli standards (as defined by the Home Front Command) are specifically designed to withstand blast waves. Every additional staircase and turn improves the protection. Therefore, an internal shelter that is not in direct line of sight from the entrance is considered very safe even against nearby impacts. ✅ Summary: Factor Effect on blast wave Sharp turns disperse the wave Stairs break up the wave Closed door blocks almost completely Horizontal + vertical distance dramatically reduces intensity

So yes, from a physics standpoint — a blast wave can begin to enter, but it will lose strength at every stage, and the chance that it will reach the shelter with dangerous force approaches zero.
Therefore the shelter is very safe even if the missile lands at the entrance to the building.

If you want, I can draw a schematic diagram of the route and mark on it how blast waves decay.