Keyless ignition systems are becoming increasingly popular as they allow consumers to enter their vehicle and start the ignition without ever having to take their keys out. These systems are convenient but they could prove tragic in certain circumstances.

As the New York Times reports, at least 28 people have been killed in the United States by carbon monoxide emitted by vehicles with a keyless ignition. At least 45 others have been injured and some of them have been left with brain damage.

The report notes keyless ignition systems are now standard on nearly half of all new vehicles sold in the United States and this poses an increasing risk as some drivers forget to shut off their engine when they park in their garage. Given how quite new engines can be, some owners simply park their car, go into their house and don’t even notice their vehicle is still running. If this happens for an extended period of time, they could eventually succumb to carbon monoxide poisoning.

Despite a growing number of fatalities, most automakers haven’t introduced safety systems which could prevent a deadly buildup of carbon monoxide. As the newspaper notes, the Society of Automotive Engineers has previously called for keyless ignition systems to alert vehicles owners when their car is still running but the keys aren’t in the vehicle or nearby.

Changes could be coming as the National Highway Traffic Safety Administration has proposed a new regulation which would require vehicles to warn owners when the ignition hasn’t been shut off. However, many automakers are opposed to the new regulation and it hasn’t gained much traction.

The news isn’t all bad as newer Ford models will automatically shut off the engine if the car has been idling for 30 minutes and the key fob isn’t inside the vehicle. Unfortunately, a number of automakers aren’t following suit even though estimates suggest adding new safety features would cost less than $500,000 a year.