Blood is extremely dangerous when carried to the blood via the lungs by inhalation, because carbon monoxide irreversibly binds to hemoglobin to form carboxyhemoglobin, so that less hemoglobin is free to bind oxygen, and fewer oxygen molecules can be transported throughout the blood. This can cause suffocation insidiously. A fire burning in an enclosed room with poor ventilation presents a very dangerous hazard, since it can create a build-up of carbon monoxide in the air. Some carbon monoxide binds to hemoglobin when smoking tobacco. Blood for transfusion is obtained from human donors by blood donation and stored in a blood bank.
Hemoglobin of the amount of oxygen in a patient's blood by an instrument called a pulse oximeter. This difference also accounts for the presentation of cyanosis, the blue to purplish color that tissues develop during hypoxia. Deoxygenated hemoglobin is paramagnetic; it is weakly attracted to magnetic fields. In contrast, oxygenated hemoglobin exhibits diamagnetism, a weak repulsion from a magnetic field. Scientists agree that the event that separated myoglobin from hemoglobin occurred after lampreys diverged from jawed vertebrates. This separation of myoglobin and hemoglobin allowed for the different functions of the two molecules to arise and develop: myoglobin has more to do