Philadelphia Tri-plex (3 unit) Fire Code?

[Matt Daley]

Buying a 3 unit property in Philadelphia. Appraiser is requiring a hard wired fire alarm to be installed. I have been looking on-line through the fire code for Philadelphia and trying to find out specifically where it says this so that I can show the seller. Does anyone have any experience? Have a link or a good resource that could provide this info? Know of any exceptions to the code? (seems like there are a lot of exceptions for other types of buildings). 

Thanks in advance.