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 Hopkins-2 carrying hemoglobin S and Ho-2, none were anemic; but, a few of those studied displayed elevated reticulocyte counts. This is measured through a blood test that analyzes the speed of production of red blood cells by bone marrow and its release into the blood. There was no suggestion of symptomatic sickle cell anemia in the family. There was a study on a three year old that was a carrier of the hemoglobin variant of Hopkins-2. The child had mild anemia and reticulocytosis, which is commonly seen in anemia. There were, however, no sickled cells found in the blood and they