Dissolved Oxygen

In freshwater rivers and streams, dissolved oxygen (DO) concentrations vary depending on season, water depth and location. Colder water holds more O2 than warmer water. Low levels could indicate more plants or animals, plant die-off or pollution.

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This is the trickiest test, and timing is super important!

1. Take out an ampoule and your sample cup. Notice the ridges in the bottom. Notice the white tip on the ampoule. This is a weak point in the glass.

2. Take a water sample as far below the surface as you can reach. Do not shake. It is more important to get sample quickly than to get exactly 25mL.

3. IMMEDIATELY put ampoule, tip down, into sample. Break ampoule end off using one of the ridges at the bottom of the sample container by pressing against ridge and pushing inward. It takes less pressure than you think!

4. Ampoule will fill with water. Once mostly filled, remove from sample and invert two times (watch the bubble travel up/down 2 times).

5. Hold tip facing upwards for 2-minutes (sand timer/stopwatch).

6. Take out your comparison chart. Place the ampoule flat between the comparison chart until you and your testing companion agree on the reading. If it’s between two values, take the half-way point.

7. Recorded your results, carefully pour water out, leaving glass tip in your sample cup. Remove tip and used ampoule and put in a WhirlPak bag (side pocket). Dispose in regular garbage when you return home.

6. Pack up your kit. Do not expose comparison chart or ampoules to light except while conducting test since the dye is affected by sunlight.

How to interpret

0-2 mg/L: not enough oxygen to support most forms of life
2-4 mg/L: only a few fish and aquatic insects can survive
4-7 mg/L: good for many aquatic animals, low for cold water fish, good for warm water fish
7-11 mg/L: very good for most cold water fish

Make sure you take out your comparison chart. Pull from the bottom. To put it back in, position under the top lip first and press downward. On sunny days, find a shady spot to compare results.

How to conduct the Dissolved Oxygen Test with the Chemets kit (4:28)

This conductivity meter can be found in…


This device has been compared to professional probes very good results.