Boc solid phase peptide synthesis is not recommended as it generally requires the use of HF to eventually cleave your resins. It works quite well and offers a number of advantages if you can dedicate yourself to proper and safe use of HF gas.
The deprotection phases generally use TFA, I'm not entirely sure what you are referring to as a closed system here, solid phase synthesis is generally an open system run in equilibrium with solvents.
Thank you Zohreh Nazarian but i found in literature that using scavengers might help in case cleavage along with the removal of protecting groups using TFA:DCM might sometimes be unproductive.?