We cannot see it, taste it, or smell it. Nevertheless, carbon monoxide is a deadly poison; it is a frequent cause of poisoning all over the world. This gaseous product of incomplete combustion displaces the oxygen molecules carried by hemoglobin throughout the body, thereby starving tissues of oxygen and causing death. Now, Azarov et al. have reengineered neuroglobin, a hemoglobin-like protein from the brain, so that it binds carbon monoxide more quickly and tightly than does hemoglobin. When CO-poisoned mice are infused with the artificial neuroglobin, it scavenges the CO, freeing hemoglobin to perform its oxygen delivery duty. The engineered neuroglobin ensures the survival of CO-poisoned mice. The half-life of CO in human red blood cells treated with neuroglobin is only 25 s, compared with a published half-life of 20 min with hyberbaric oxygen, the best treatment currently available. Engineered globins show encouraging promise as antidotes for this lethal gas.