Abstract: At 07:30 a.m. on August 17, 2018, Employee #1, a Supervisor, was cutting a concrete floor (indoors) using a gas-powered saw, during a plumbing construction project. Other coworkers, including: Employee #2 performed work adjacent to this operation. The Employer outfitted the concrete saw with an oxidation catalyst, exhaust scrubber, which is required to reduce dangerous concentrations of harmful Carbon Monoxide (CO) and particulate matter; however, no atmospheric monitoring was performed during the first hour of the operation to evaluate exposure levels. The employer mandated use of N95 filtering facepiece respirators to reduce exposure to silica; however, workers were untrained, as to the limitations of the N95 respirator, e.g., does not offer protection against chemicals, gases, or vapors, such as: "sewer smells", etc., in the work environment. The employer installed two large circular fans, as a means for exhaust; however, an effective ventilation system was not used to eliminate Carbon Monoxide from the work area. In consequence, Employee #1 was hospitalized after being overexposed to CO and Employee #2, Plumber/Coworker, exposed during work task performed adjacent to CO emissions, sustained low-level exposure to CO and suffered bodily symptoms, such as: dizziness, drowsiness, and weakness.