Vibrations in laboratories and in workshops for high precision technologies (HPT) in single and multistorey buildings originate from steady and transient excitation sources and propagation through the building's foundation and structure. The paper is concerned with problems of the high efficiency vibration isolation systems. An answer to the question what is said to be passive and active isolation is given in a new way. For an example of self developed semi-active system it is shown that excitations from the floor may be damped only by a fully active isolation. A new active model is being constructed and the paper gives some results of the computer simulations.