Can I childproof a fire escape window

[Guest Karen Forsythe]

We have a fire escape window on our upstairs landing and I've just found out my 3 year old twin girls can open the window. As there is no lock or anything on this window, is there anything we can fit to childproof this window without compromising fire safety? 

[Tom Sutton]

 Approved Document B (Fire Safety) Vol 1  paragraph 2.10. states

c. Locks (with or without removable keys) and opening stays (with child-resistant release catches)
may be fitted to escape windows.
d. Windows should be capable of remaining open without being held.

Check out Approved Document B (Fire Safety) Vol 1

[Guest Karen Forsythe]

Thanks for your help ?