Locked in a Jeep 4x4 in the parking lot of McMaster Children's Hospital, Dr. Anthony Crocco is starting to look a little weary.

The windows are shut tight. The engine is off, and so is the air conditioning. Outside, the temperature is 30 C, but with the humidity, it feels like 37.

Inside, Crocco's skin is getting clammy. The sweat trickles down his back. For 15 grueling minutes, he sits in the stifling 40 C heat. But he's in there to make a point — when parents leave kids in hot cars, they're gambling with their lives. And this is a demonstration.

"The good news today is I can get myself out of that car at any time," Crocco said after the experiment Wednesday.

"I've got water standing by. I'm being watched by paramedics. But for a child strapped into a car, they don't have the ability to modify their environment."

Crocco's point is relevant. Last year, Hamilton paramedics responded to 65 heat-related calls, and 17 of them were kids, said paramedic Michelle Greenspoon. Two were kids who needed emergency treatment because they were accidentally locked in hot cars.

Anthony Crocco sits in a hot car0:18

The dangers vary, Greenspoon said. When trapped in a hot car, a person's heart rate increases, as does their breaths per minute. They sweat, which leads to dehydration. Eventually, organs shut down.

Crocco, an emergency pediatric physician, is healthier than most. He's 44 and does triathalons. After about 15 minutes in the car, his heart rate increased by about 10 beats per minute, and his breathing by four or five breaths per minute. That's not bad, Greenspoon said.

Anthony Crocco

Paramedics inspect Anthony Crocco after he gets out of a hot car after 15 minutes. (Samantha Craggs/CBC)

But a child's body temperature rises four or five times faster than an adult's, she said. And the vehicle wasn't in direct sunlight.

Crocco said it still wasn't pleasant.

"The first thing I experienced was discomfort, where I would prefer not to be in this hot environment," he said. "Then very quickly, I started to sweat."