 Carbon monoxide is not toxic to all forms of life . Its harmful effects are due to binding with hemoglobin so its danger to organisms that do not use this compound is doubtful . It thus has no effect on photosynthesising plants . It is easily absorbed through the lungs . Inhaling the gas can lead to hypoxic injury , nervous system damage , and even death . Different people and populations may have different carbon monoxide tolerance levels . On average , exposures at 100 ppm or greater is dangerous to human health . In the United States , the OSHA limits long @-@ term workplace exposure levels to less than 50 ppm averaged over an 8 @-@ hour period ; in addition , employees are to be removed from any confined space if an upper limit ( " ceiling " ) of 100 ppm is reached . Carbon monoxide exposure may lead to a significantly shorter life span due to heart damage . The carbon monoxide tolerance level for any person is altered by several factors , including activity level , rate of ventilation , a pre @-@ existing cerebral or cardiovascular disease , cardiac output , anemia , sickle cell disease and other hematological disorders , barometric pressure , and metabolic rate . 
