An apparatus for introducing gas into liquids, which does not use an injector operating on the Venturi principle, comprising: - a flow tube which has a feed line for the liquid to be fumigated and at least one outflow line for the gas/liquid mixture, - a chamber (25a,25b,25c,25d); a line and a displacement pump operating in a sucking manner to introduce a partial amount of the gas/liquid mixture from the flow tube via the line into the chamber (25a,25b,25c,25d) via the displacement pump. - a return line to feed the gas/liquid mixture from the chamber (25a,25b,25c,25d) via the displacement pump under pressure into the flow tube,wherein the return line ends in the flow tube with a drain; - a feed line for the gas to be introduced, with which the chamber (25a,25b,25c,25d) is provided; - and a valve which can be switched such that the liquid stream from the feed line for the liquid to be fumigated, into the outflow line for the gas/liquid mixture is throttled or stopped, and the gas/liquid mixture is led into the circulation via the displacement pump until an optimal enrichment is reached, wherein the chamber (25a,25b,25c,25d) consists of a cylindrical bore in the configuration of a pointed cone, and wherein at the cone, the beginning of the return line is adjoined which is chosen in its dimension such that a vortex for reducing the size of bubbles is produced by increasing the flow rate inside the cylindric bore. - a flow tube which has a feed line for the liquid to be fumigated and at least one outflow line for the gas/liquid mixture, - a chamber (25a,25b,25c,25d); a line and a displacement pump operating in a sucking manner to introduce a partial amount of the gas/liquid mixture from the flow tube via the line into the chamber (25a,25b,25c,25d) via the displacement pump. - a return line to feed the gas/liquid mixture from the chamber (25a,25b,25c,25d) via the displacement pump under pressure into the flow tube,wherein the return line ends in the flow tube with a drain; - a feed line for the gas to be introduced, with which the chamber (25a,25b,25c,25d) is provided; - and a valve which can be switched such that the liquid stream from the feed line for the liquid to be fumigated, into the outflow line for the gas/liquid mixture is throttled or stopped, and the gas/liquid mixture is led into the circulation via the displacement pump until an optimal enrichment is reached, wherein the chamber (25a,25b,25c,25d) consists of a cylindrical bore in the configuration of a pointed cone, and wherein at the cone, the beginning of the return line is adjoined which is chosen in its dimension such that a vortex for reducing the size of bubbles is produced by increasing the flow rate inside the cylindric bore. - a return line to feed the gas/liquid mixture from the chamber (25a,25b,25c,25d) via the displacement pump under pressure into the flow tube,wherein the return line ends in the flow tube with a drain; - a feed line for the gas to be introduced, with which the chamber (25a,25b,25c,25d) is provided; - and a valve which can be switched such that the liquid stream from the feed line for the liquid to be fumigated, into the outflow line for the gas/liquid mixture is throttled or stopped, and the gas/liquid mixture is led into the circulation via the displacement pump until an optimal enrichment is reached, wherein the chamber (25a,25b,25c,25d) consists of a cylindrical bore in the configuration of a pointed cone, and wherein at the cone, the beginning of the return line is adjoined which is chosen in its dimension such that a vortex for reducing the size of bubbles is produced by increasing the flow rate inside the cylindric bore.