Use Thermo Scientific™ COD (Chemical Oxygen Demand) Calibration Standards with Orion™ AQUAfast Colorimeters such as AQ4000 Advanced Colorimeter and Orion AQUAfast II AQ2040 Colorimeter. Orion colorimeters, which measure COD chemistries, are ideal for environmental and wastewater monitoring. Use these calibration standards to check operations prior to using the instruments.