Fire officials say two people died in the house and one later died at Elmhurst Hospital.
The Uniformed Firefighters Association says precious response time was lost when firefighters were sent to the wrong address.
Under the new Unified Call Taker system, 911 operators dispatch firefighters directly instead of first transferring calls to the Fire Department.
In this case, fire officials say a dispatcher entered the wrong address by mistake, sending one unit down the street and delaying it about 40 seconds.
The UFA says errors are common with the new call system and even small delays can cost lives.
"Had we been on the time, we can't swear we would have saved all lives, however, we didn't have the opportunity to. A couple minutes or more was lost in time, which allowed this fire to create more heat, more smoke, which unfortunately may have led to the death of three people," said Leroy McGinnis of the UFA.
Investigators believe the fire was caused by a boiler that exploded.
The buildings department says the two family home had been illegally converted into a five-family home, and issued three violations and a vacate order.