A member of the halogen family of sanitizers, it's use in swimming pools is in the elemental form of a gas, liquid, granular, or tablet compound. When added to water it acts as an oxidizer, sanitizer, disinfectant, and all around biocidal agent.
That portion of total available chlorine left over when free available chlorine is subtracted. The measure of chlorine which has already attached itself to other molecules or organisms. Most of this is made up of chloramines.
Free Available Chlorine is that which is active, not combined with an ammonia or a nitrogen molecule, and ready to react to destroy organic material.
The sum of combined and free chlorine levels. With a DPD test kit, one determines free available level, then total available. The difference, if any, is the level of combined chlorine.
The quantity of free available chlorine removed during the process of sanitizing. The amount of organic and non-organic material contained in the water will demand a certain level of oxidizer to be destroyed.
A miniature chlorine factory. This device creates its own sanitizer for your pool.