Advice of Scholars - NECESSARY REASONS FOR BREAKING NAMÂZ

Namâz must be broken in order to save a person who screams for help, to save a blind person who is about to fall down into a well, to save a person who is about to burn or drown, or to put out a fire.
When your mother, father, grandmother or grandfather calls you, it is not wâjib for you to break a fard namâz, but it is permissible; yet, you must not break it if it is not necessary. But supererogatory namâz [even the sunnats] must be broken. If they call for help, it is necessary to break the fard namâz, too. If they call you although they know that you are performing namâz, you may not break even the supererogatory namâz. But if they call you and do not know that you are performing namâz, you have to break it.