Many newer model cars utilize high-tech modifications such as the keyless push-button ignition system. Some argue that the feature makes the driving experience easier, but others are speaking up by pointing out the hidden dangers of push-to-start systems.

NBC News reports that the keyless systems are fatally flawed, according to critics. Sean Kane, president of Safety Research and Strategies, says that the current keyless models have “an inherent design defect,” claiming that manufacturers have changed the relationship between the driver and the key without disclosing the several safety hazards.

The main concern is that many people do not always remember to turn their car off. Critics claim that it is much easier to forget to push the button than it is to take a traditional key out of the ignition. If the car is left running, the carbon monoxide released from the tailpipe can easily seep into your home through an attached garage or open ducts. Carbon monoxide inhalation can cause illness or even death.

“We have documented at least 19 fatalities that are specifically attributed to keyless ignition vehicles since 2009 and 25 more close calls,” said Janette Fennell, founder and president of the safety group KidsAndCars.org. “As more keyless ignition vehicles are sold, we are going to see these predictable and preventable injuries and deaths increase.”

Kane points out that in most keyless ignition vehicles, you can exit the car with the fob in hand. Simply leaving the vehicle with the key fob will not turn stop the car: the engine will continue to run until the fuel supply is depleted if not deliberately turned off. He says, “You need the fob to start the vehicle, but it plays absolutely no role in turning it off.”

In November 2015, a family of six in Washington had to be rushed to hospital and suffered the effects of carbon monoxide poisoning. The father accidentally left his Toyota van running in the garage; he took the keyless start fob in the house with him but forgot to turn the engine off. When firefighters arrived, they found incredibly high levels of carbon monoxide in the house. The van had been running all night long.

Aside from the safety issue, keyless start systems are not as reliable as standard metal keys. Many auto repair shops see these push-to-start ignitions short out and drain the battery, causing a host of electrical problems. Cars have complicated electrical systems and one malfunction can affect the entire vehicle.

“I do believe these type of vehicles are dangerous and using a standard key instead would prevent a host of unnecessary problems faced today with keyless systems,” said Ray Fannin, Owner, A&J Automotive, Inc.

As more and more manufacturers are opening their eyes to the flaws in the keyless systems, efforts are being made to slowly phase them out. Instead of making them standard, many auto manufacturers are beginning to offer them as an option.

NBC News reached out to automakers to get their input on keyless ignition problems. In an email, Wade Newton, director of communications for the Alliance of Automobile Manufacturers said, “The industry continues working with a standards-setting body to further develop best practices.”