Selfmixing technique has many disadvantages when compared to the standard gas laser based LDA. Nevertheless, there are some peculiarities of the method which became very profitable when some specific measurement conditions are considered. Such situation arises when the measurement is to be carried out in hot air flow inside of large compartment. The background, construction and technical characteristics of two dimensional probe based on the laser diode module are presented in the paper. The developed water-cooled sensor is used to build up the multipoint velocity measurement system, which is used to study the high temperature air flow inside the large scaled model of the nuclear power plant containment. The data are needed to verify the results of the flow field computational simulations.