The Floor slab tool 
allows to place intermediate floor slabs between floors.
To activate the Floor slab tool, click the button on the toolbar or navigate to Tools | Drawing | Slab.
You can also use the* **Alt + O** hot key.
You can place floor slabs in the following ways:
- Manually specify the area where the floor slab must be located. The procedure is similar to drawing a wall in the shape of a polygon.
- Use the Create automatically button to create a rectangular floor snab with dimensions that encompass all elements of the scene.
If the floor slab does not act as a barrier to the spread of dangerous fire factors, it can be disregarded during fire dynamics simulation. For more details, see Ignoring Objects in Fire Dynamics Simulation