The classic carbon monoxide fatality in Hollywood was Thelma Todd's accidental death after being dropped off from a late party for walking up flights of stairs to a closed garage around 4:30 AM on the morning of Sunday, December 15, 1935. Four books have been written about the first blonde bombshell comedienne in talking pictures, and there has been much speculation that she might have been somehow murdered or committed suicide.
My research aside from the four books written makes it clear though that she succumbed to carbon monoxide fumes while revving up her powerful but quiet 1932 Lincoln KB Dual Cowl Phaeton V12 in less than two minutes, possibly after taking a nap in the back seat until daybreak in her full length mink coat. The temperature at that time in the morning was a record low 38 degrees Fahrenheit in Santa Monica, California on the seacoast according to the archival National Weather Service data, so she had to warm up her car in what was essentially a giant refrigerated compartment before she could leave it idling to slide open the garage door to drive it off. The garage was new and seemingly too well insulated for carbon monoxide poisoning to take place, let alone that quickly, or so she thought. She never had a chance.
After her maid discovered her body seemingly asleep behind the wheel of her car late that Monday morning, an LAPD detective tested out how long he could tolerate staying inside that closed garage with the engine idling, but not revving up, and was pounding on the door to be let out in 90 seconds, coughing with eyes watering. Carbon monoxide in an enclosed space with a car that powerful in that era was quickly deadly.
Previously that summer, there had been a Dick Tracey comic strip running in the Los Angeles Times which had gangster villains about to asphyxiate some trapped victims in a sealed room with the exhaust of a car's racing engine being funneled into the room, but the dialogue from the gangsters to their trapped quarry stated that they'd be dead in about an hour. Turned out that was fictitiously generous compared to how quickly Thelma Todd succumbed.
Coroner's conclusion was that it was an accidental death. Decades later, a former classmate of my two brothers ran a hose from the exhaust pipe of a car into the vehicle, and deliberately took himself out with carbon monoxide.
In this day and age, establishing the presence of dangerous carbon monoxide levels is simple enough with a detector alarm run on a 9 volt battery.
