I know about necessary egresses and about quick release mechanisms for window bars and about alarms vs. window bars...  I want to figure out the answer to a specific question.  

Is there a legal precedent for the following?.... Landlord rents a property to Tenants. Property has bedrooms on the 1st floor which have window bars.  The window bars are able to swing open, unless locked.  Tenant has the option to either leave the window bars 'swing-able' without a lock (essentially just for use as a visual deterrent)...or they can add a key or combo lock to the bars to keep them more secure (key/combo lock is NOT OK for fire codes).  The Lease states that the window bars are there only for visual deterrent and that if a Tenant chooses to lock them, the Tenant is liable for any fire hazard that results.  What happens if there's a fire and the Tenant has locked themselves in without a code or key? Who is liable?