well the systems we work with they aren't inside all piping is out side

Secondly soap and water is whay we use if there is still any leaking even after passing the lighter test, usualy the lighter test finds any leaks with flares, and realy it's only the big leaks we are worried about, microscopic leaks no one bothers with, but in a refrigeration system it changes you want zerro leaks, so first flame to find any obvious leaks for your flares then soap and water to find any small leaks all ways do it out side where there isn't a whole ton of air flow but still a light breeze.