Legal obligations need to be respected for fire safety. Depending on the building class (use, surfaces, heights), the requirements are specified for every component.
In lightweight steel framing, fire protection requirements are regulated by the amount of layers. For example, a planking with 2 x 15 mm hard gypsum board will satisfy the imperatives for a REI 90 wall.
The planking protects the profile from temperature effects and allows them to keep the required duration of protection (30, 60 or 90 minutes).
The illustration shows a REI inner wall with 2 x 20 mm Knauf Fireboard.