Answered by: Shaykh Shafiur Rahman
Salam, I am worried. I wanted to ask what should you do if the semen dropped on the carpet and in the same room you pray namaz how should you clean the semen and make the room pure?
In the name of Allah, the Most Gracious, the Most Merciful
If it is a removable rug or something similar then the whole rug should be washed and cleaned properly until the semen is removed.
If it is carpet fixed to the floor of the whole room then one would need to wash and clean the affected area for example with water and preferably detergent to remove the semen. 
Only Allah knows best
Written by Shaykh Shafiur Rahman
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
ص314 – كتاب الدر المختار وحاشية ابن عابدين رد المحتار – باب الأنجاس – المكتبة الشاملة الحديثة