Pyrotechnics is common to use in conjunction with model miniatures to create the illusion of buildings blowing up and alike. It involves using explosives to mimic the effects of things like bombs, and there are certain ways in which model miniatures have to be constructed in order to get the dramatic results we see on tv. Firstly models used for this type of action shoot need to be built as big as possible. Frequently and so that the model will explode more easily they get made in sections which are simply laid into position.
Lots of dust and debris needs to be provided at the source of the explosion. One method is the use of cement dust which can be blown out using compressed air.