Chicago Smoke Detector Compliance

[Bryan K.]

Are there any Chicago landlords out there familiar with smoke detector code in Illinois/Chicago?  My understanding is that all smoke detectors need to be hardwired near each bedroom.  I just bought a building and, for whatever reason, none of the smoke detectors are hardwired.  I cannot figure out for the life of me why they didn't just hardwire them during construction.  The only way to hardwire them now is the open up the walls.  Is there an exemption I'm missing?  Or are some landlords just cheap and opt to go with battery smoke detectors notwithstanding the law? 

On a similar note, if anyone can refer me to a cheap smoke detector installer in the city, I would appreciate the referral.  Thanks!