Greiner has consulted on and investigated several cases of poisoning from car fumes, some resulting in death. Concentrations in the exhaust can be more than 80,000 parts per million. Concentrations so large fill the garage with carbon monoxide in a very short time even with the door open. Once the car is backed out of the garage and the garage door closed, large concentrations of gas still remain trapped in the garage. In a house built with an attached garage, part of the gas then seeps into the house where it remains for hours.
Carbon monoxide reduces the oxygen supply to the brain, causing carbon monoxide intoxication.
At high concentrations, such as produced in the exhaust of a cold engine, carbon monoxide intoxication occurs in only a few minutes, leaving those poisoned incapable of realizing they are poisoned, and unable to protect themselves. Carbon monoxide poisoning can happen to anyone, although children, the elderly and those with health concerns are especially susceptible. Greiner conducted an investigation at a central Iowa home where the family was diagnosed with carbon monoxide poisoning and treated with oxygen. The husband typically opened the overhead garage door in the attached garage, started his small pick-up, let it warm for one or two minutes, drove out, shut the garage door, and left for work. His wife, who works in a home office, often developed late morning headaches.