Answer:
This is how you change the setting on a BD 524972 instant ear thermometer:
When the unit is off, press and hold the blue start button at the top of the unit. Then while still holding the start button, press and hold the ON/Memory button (you should now have both buttons pressed). The display will power on and you will see the setting toggle from celcius to fahrenheit. Repeat the entire process in order to toggle the setting back to celcius.