But ABC7 has found that sometimes these devices may not be close by, costing valuable time in an emergency.
Softball coach Rich Keller is alive because an AED was on a softball field in Schaumburg - and an athletic trainer knew how to use it - when Keller collapsed last month with a heart attack at the end of a game.
"I think it goes without saying. Without an AED device nearby, I wouldn't be sitting here talking to you today," said Keller.
"The greatest survival benefit is when that collapse to shock interval is a small as possible," said Heather Prendergast, MD, president of the Illinois College of Emergency Physicians.
Dr. Prendergast has studied the availability of AEDs at high school athletic events across Illinois.
"They should be accessible within a minute or two," Dr. Prendergast said. "They can't be somewhere where it's going to take five minutes to get to the AED."
"We have them right across the street, so we can go in the doors across the street," said Chris Cassidy, Whitney Young High School athletic director.
The AEDs for Chicago's Whitney Young High School are kept inside the school buildings.
As Cassidy showed ABC7, sometimes they're locked in offices. An AED in the coaches' office had clothes piled on top and TV cables hanging in front of it. Another was locked in an office down a hallway. A third was kept by the school's pool.
"We're just try to keep it in a central location so we know where to get it," said Cassidy.
In fact, ABC7 found that Chicago Public Schools typically keep all AEDs inside school buildings -- and sometimes that's far away from the athletic action.
During a Lincoln Park High School baseball game at nearby Oz Park, the closest AED was about a football field away inside the school building, even though there was a trainer present.
At Douglass High School on Chicago's West Side, games are played at Levin Park, more than four blocks from the school.
At Phillips High School on the South Side, boys' baseball games are played at Ellis Park, about a half a mile away from the school's AEDs.
"That's a big concern, because, again, it creates a false sense of assurance," said Dr. Prendergast.
"Ideally, you would want that defibrillator to be where it's accessible," said Dr. George Chiampas.
And not only accessible, but in trained hands. Dr. Chiampas is leading an effort to train as many people as possible how to use AEDs.
A training video, produced by a team of Northwestern medical students, is designed to teach middle school students.
"The reality is everyone needs to know how to use it," said Dr. Chiampas.
"If someone had to go into the building and find one and bring it back out, I think it would've been too late by then," said Brittany Moll.
Moll was there when her father, Rich Keller, collapsed.
The AED at Schaumburg High School is kept in an outdoor cabinet near the playing fields whenever there's a game or practice.
In Rich Keller's case, the device and trained hands made a life or death difference. And he got to meet his new grandson born just 12 days after his heart attack.
"I truly remind myself every single day that I don't need to win the lottery because I already did," Keller said.
Chicago Public Schools stress that all football games and some other events are held in stadiums outfitted with AEDs. Officials from the district say that for the sports that the AEDs are kept inside they can reach them in time if they were ever needed.
For games played at public parks, those facilities are not required to have AEDs but some have installed them anyway.
Legislation requiring the CPR AED training video to be shown to all middle school students is working through the legislature.