) 

  
 ::Yet the question still has not been answered. I work around older IC Engines without Catalytic converters. Even with good ventilation there is still some level of CO in the area. Without hyperbaric treatmenthow long does it take low levels of CO bonding to dissipate. Ie. If one were exposed to an atmosphere of 20 PPM for 3 or 4 hours daily for 3 or 4 days, how long should one wait before again exposing ones self to those levels again? (My work around old engines is a hobby, I can take extended breaks doing other things between times that I require them to actually be running for testing.) My Google searches have not yet turned up a substantial answer. :[Gerald Livingston] (CST