Dissolved Oxygen Test Kit (0.65-8.0 mg/l as O2) No. of Tests – 250 Dissolved oxygen (do) refers to the amount of oxygen that is present in water. Do is important for maintenance of sewage treatment units. D.o. is essential for the aquatic plant and animal life. Do is detrimental in boiler systems because it leads to corrosion in boiler systems. Do analysis measures the amount of gaseous oxygen (o2) dissolved In an aqueous solution DO measurement is a tricky business, but our kit makes testing easy and simple.