A lethal gas normally linked to faulty boilers and car exhausts plays a vital role in the digestive system, say researchers.
Traffic fumes contain carbon monoxide
They say harnessing carbon monoxide as a treatment could cut the amount of time patients spend in hospital after operations, and help people with certain digestive disorders.
Carbon monoxide is produced by the incomplete burning of fossil fuels.
It is dangerous because it can interfere with the mechanism the body uses to carry oxygen around the bloodstream to every tissue that needs it.
It binds to the chemical in red blood cells that normally binds to oxygen molecules starving the body of oxygen, even if enough is getting into the lungs.
It is odourless and tasteless - many of its victims are unaware they are being poisoned.
However, experts at the Mayo Clinic in Minnesota, US, have found he body actually makes its own carbon monoxide within the gut.
It appears to help regulate the squeezing action which pushes matter along the intestine.
Areas with more carbon monoxide have smooth muscle that squeezes less vigorously, while those areas with less squeeze more tightly.
Early studies suggest animals given a dose of carbon monoxide prior to abdominal surgery recover intestinal function far more quickly.
Dr Gianrico Farrugia, who led the study, said: "This is the number one cause of prolonged hospital stays after abdominal surgery.
"Carbon monoxide is a potent anti-hypertensive and anti-inflammatory agent, and can prevent kidney damage after surgery."
Now the scientists are working on a way to deliver the gas to correct part of the intestine at the correct time - perhaps with compounds that slowly release carbon monoxide.
However, they concede there is a "long way to go" before the prospect of drugs to aid people with intestinal "motility" problems can be helped.
The study was published in the journal Proceedings of the National Academy of Sciences.