If you rent your property to 3 or more occupants that are not from 1 household then it is classed as a HMO there are a few things that you should consider concerning the health and safety of the occupants.

All final exit doors including any doors on the exit route should be keyless, in the event of a fire and panic sets in trying to find a key can be life threatening.

Fire doors should not be propped open as these are designed to slow down the spread of fire and to confine the fire to single areas of the property, as an alternative to having the doors propped open why not fit a sound activated retainer that automatically releases the door to close on the sounding of a smoke detector / fire alarm, an example can be found here.

Windows designed as fire escapes should be kept in good working order and again accessible without the use of a key.
The locking mechanism should be in working order and the window should open fully but most importantly the tenants should be familiar with the use of the window, there is no point in having a escape plan if you can not operate the window. 

Should you need any help to make your property fire regulation compliant get in touch.