tharmal and the biological shield.

Biological Shield: This shield are most developed on our surrounding. that's  we are told it is a good behaviour of natural atmosphere.
For Example:- Our human body are protected by skin and skin are made by biological component. in our body have very immunity developer anti body and antigens. So, our body protect form other harmful virus and germs. same to our earth are protected form other useful gasses and other sources. 



Thermal Shield:  A layer, or layers, of high-density material located within a reactor pressure vessel or between the vessel and the biological shield to reduce radiation heating in the vessel and the biological shield.