Odd in my office complex courtyard , that when I had to use a dry chem fire extinguisher to put out an ash can because idiots put lit cigs in the can, I sprayed directly into the fire and the dry chem didn't blow back in my face. Perhaps it may have been windy that night at MK, who knows..N95 masks keep out airborne particulate matter and liquids. They do not protect against fumes.
Nitrogen or CO2 are the most common propellants for dry chem fire exringuishers. A N95 would not prevent inhalation of these gases.
To protect from fumes or gases, a true respirator (which requires fit testing) with appropriate filtration is required.
However, you would be correct that an N95 would provide protection to the wearer from inhaling the powder extinguishing agent in the dry Chem fire extinuisher.