Google is your friend.....
I googled "opening bae jetstream door" and the 4th choice is a pdf file from brandweer schiphol (fireservices schiphol) giving (in English) quite a detailed description of what would be important features for fire and rescue. Admittedly most items are discussed in relation to someone on the outside of the aircraft.
The operation of the door however seems straightforward - pull the handle out and rotate down in direction of the arrow. I imagine it would be the same on the inside except in mirror image.
Plus there are either one or two emergency exit hatches - the overwing windows that can also be opened from inside.