Chemical use of oxygen (CHUO) means a use of oxygen needed for all substances’ oxidation. Not only those which can be biologically degraded.CHUO is an established degree of water pollution with organic and oxidizable anorganic substances.

Chemical use of oxygen is expressed as a weight concentration of oxygen matching the use of permanganate ions on predetermined conditions.

CHUO is being established by sodium permanganate (KMnO4) titration.

CHUO is a value of nonspecific group establishment which serves for an estimation of organic pollution.

It points to a possible drinkable water pollution in wells or other locations by animal or vegetal substances.

Limit of CHUO is 3 mg/l.