It’s hot outside, but inside a car that's not running, it can be an oven. When the temperature is 88 degrees outside, a closed car will be 99 degrees in 10 minute. In 20 minutes it will be 117 degrees. During a typical Texas summer, it’s likely to be 100 degrees outside by noon.

Every summer children are left in hot cars and die. These are all preventable deaths.

Products designed to prevent parents and caregivers from accidentally leaving babies and toddlers in cars have become quite popular. But a review of 18 commercial devices, including systems integrated into a car, shows none works well enough to rely on.

“While these devices are very well-intended, none of them are a full or complete solution for making sure a parent never leaves a baby behind in a hot car,” David Strickland, administrator of the National Highway Traffic Safety Administration (NHTSA), told reporters.

NHTSA says 527 children have died of heat stroke after being left in cars since 1998, or about 38 every year. “In 2011, 33 such cases were reported,” NHTSA said in a statement, citing Jan Null of San Francisco State University, who tracks the reports.

“We aren’t only talking about the 98 degree day when you leave your child for eight hours while you are at work,” said Dr. Kristy Arbogast of The Children’s Hospital of Philadelphia, who led the research. “This can happen very quickly.”

Arbogast and colleagues reviewed every product they could find: pads that sense if a child is in his or her car seat; devices that detect whether the seatbelt is buckled; chest clips that attach to the restraint; sensors that can tell if the back door was opened; and alarms that remind parents to check. They thoroughly tested three of the devices.

“The devices were inconsistent and unreliable in their performance,” they wrote in their report, commissioned by NHTSA and released on Monday.

“They often required adjusting of the position of the child within the child restraint, the distance to activation varied across trials and scenarios and they experienced continual synching/un-synching during use,” they added.

Sometimes a cell-phone interfered with the device, and spilled juice or milk could knock some out completely. “In sum, the devices require considerable effort from the parent/caregiver to ensure smooth operation and often that operation is not consistent,” Arbogast’s team concluded. “None directly address the root cause of the hot environment that led to the potential for heat stroke.”

Many relied on an alarm that was on the car’s key fob and that worried Arbogast. “What if my husband was taking the child and I forget to give him the key fob?” she asked.

“Most important, it should be noted that these devices which integrate into a child restraint would not be applicable in scenarios where the child is playing and gets locked in the vehicle (30 percent of fatalities) or in a scenario where the parent/caregiver intentionally leaves the child in the vehicle (17 percent of fatalities),” the report notes.

Parents have seen the reports of these tragedies and are looking for help to protect their child. “There has been a recent rise in demand for technologies to prevent these deaths by reminding the caregiver that the child is in the car, as about half of these children have inadvertently been forgotten,” the report reads.

Experts suggest that parents and caregivers “layer” their routine by adding steps to exiting the car. Put your purse or briefcase in the backseat as a reminder. You might even want to consider putting one shoe in the back seat, anything that will remind you to look at your child before you leave the car. 

Other suggestions parents or caregivers might want to try:

- Leave a large teddy bear in the front seat as a reminder.

- Setting an alarm on your cell phone to remind you to check for your child. Set it for about the time it usually takes to arrive where you are going.

- Having a routine with the child’s caregiver. “If it is well-established that when your child shows up in the morning, if they don’t show up within 10 minutes of that time the daycare provider calls you or sends a text,” Arbogast suggested.