Hello Friends! Smoker inhales Carbon monoxide and it is thousand times more reactive than Oxygen due to its triple bond formation with haemoglobin which is a protein molecule having iron at centre. Normally in inhaling of oxygen haemoglobin becomes oxyhomoglobin(single bond) and carries fresh oxygen to cells where oxygen is detached and Haemoglobin comes back to take fresh oxygen again. When one smokes haemoglobin makes carboxy haemoglobin ( triple bond) .In this case carbon monoxide does not detach from haemoglobin.So consequently excess carboxyhomoglobin accumulates. Is some carbon monoxide left without getting attached to haemoglobin and hence more harmful to cells. In the exhaled gas of a smoker what is there to do more harm to passive smokers. Please refine the above sequence of logic. I am not clear about the process.