Abstract: At approximately 11:30 a.m. on March 23, 2017, two employees were cutting through a concrete floor to replace a sewer pipe inside a hallway of a condominium complex. The employees were using a gas powered concrete saw. The concrete saw was equipped with a Foley Industrial Engine Exhaust Purifier which was supposed to reduce carbon monoxide to a safe level. The exhaust purifier which was a bolt on a catalytic converter would only reduce carbon monoxide levels to 5,000 ppm per information from the manufacturer's website information. The employees began to experience light headedness, headaches, disorientation, and tingling in hands from exposure to the exhaust from the gas powered concrete saw. The employees were exposed to carbon monoxide levels which exceeded 50 ppm as an 8 hour time weighted after just 30 minutes of exposure. The fire department measured carbon monoxide levels of over 300 ppm. Carboxyhemoglobin levels two hours after exposure were 19.5% and 18.2%. The employees did not lose consciousness and were not hospitalized.