Johns Hopkins researchers have shown that brain damage was reduced by as much as 62.2 percent in mice who inhale low amounts of carbon monoxide after an induced stroke. The scientists say that although carbon monoxide (CO) gas has a long reputation as an odorless, colorless cause of organ damage and even death, there is now evidence that it can protect nerve cells from damage. Some of the brain damage associated with stroke results directly from a cut-off in blood supply to nerve cells.