asbestos removal

People are going to pull down an old building containing asbestos and i would like to know after how much time will the traces of asbestos disappear in the air.

This is a difficult question to answer without knowing the type of asbestos materials present, the way the building will be demolished and the duration of the works. Generally asbestos fibres can remain airborne for upwards of 12 hours. If the work is external the material will generally quickly desperate, however if re-disturbed the material can become airborne once more.