To measure different metabolism parameters (oxygen consumption, for example) of living organisms a special device is needed. This measuring device is called respirometer. Today's respirometers technology offers a great number of different principles on which real devices and systems are based. All these methods give different accuracy of measurements and some of them are easier to use. During the process of respiration (breathing) each living being consumes oxygen and produces carbon dioxide. The amount of these gases being exchanged is measured by respirometer. A usual respirometer has a special chamber in which a living organism is placed for gauging. There are many different ways to measure the oxygen consumption. One of them and, probably, the very first is believed to have a direct connection with respirometers. Measurements are performed by comparison. The amount of oxygen a living organism consumes is equal to the amount of carbon dioxide it produces. This means that to measure the oxygen consumption you can calculate the amount of carbon dioxide a living organism produces (they are equal). So, the method is used to absorb all the carbon dioxide and determine the margin of the overall volume. Alongside the organism, which oxygen consumption is to be measured, a special substance that is able to absorb carbon dioxide is also placed into the chamber. Such materials as potassium hydroxide (usually cotton wad soaked with it is used in the chamber) or soda lime can be used as absorbent of carbon dioxide. And a device that measures the pressure in the chamber is attached. The simplest device is a U-shaped tube with a liquid inside. As the pressure in the chamber changes the level of liquid in the U-tube also modifies. By this difference in the levels in the two sections of U-tube actual amount of consumed oxygen can be easily calculated. But since the time the first models were introduced, respirometers technology has changed greatly. These days there are specially designed probes that allow measuring the amount of oxygen directly and, thus, suitable for respirometers technology. For example, in aquatic respirometers a dissolved oxygen probe is used and it allows determining the amount of oxygen in water. So, if it is needed to measure respiration of any aquatic organism respirometer will only include respirometry chamber, dissolved oxygen probe inserted into this chamber and a computer to get the results from the probe. Also a pump can be used to provide water circulation in the chamber, but the cycle of water must be closed when measuring is performed. Methods, sensors and respirometers technology are is still being developed and there are many new efficient devices to be designed in the future. The number of companies, which produce respirometry equipment on the modern market, is not that big but they usually offer a great range of different devices for all sorts of respirometry measurement. These firms will also provide you with all the needed information and technical support of the equipment they offer.