A concealed sprinkler including a body having a proximal portion and a distal portion. The distal portion includes an annular wall defining a chamber and an opening in communication with the chamber. A deflector assembly is disposed within the chamber. A trigger assembly having a lever assembly engaged with an inner surface of the annular wall supports the deflector assembly in the first position, the trigger assembly including and a thermally rated plate assembly having a lip portion to substantially circumscribe and substantially cover opening and chamber.