Last week two men working in the basement of a house in Evanston, Illinois were rescued by paramedics and taken to the hospital after being sickened by carbon monoxide fumes from the gas-powered cut saw they were using. First responders referred to the tool generically as a “K-12 saw”, a rescue saw made by Husqvarna and used by many fire departments. The men were probably cutting through a concrete slab with some other brand/model of cut saw—since construction workers are unlikely to use a rescue saw.
Tests found carbon monoxide levels of 450 ppm in the basement and 150 ppm upstairs. Under federal standards 35 ppm is the maximum allowable concentration. According to the CDC, prolonged exposure to concentrations over 150-200 ppm can be fatal. If you want to cut concrete indoors, go with an electric saw or do what it takes to provide adequate ventilation. Read more.