How do you deconsecrate an area, building or holy thing, no longer used for a holy purpose ?
Once an item or a place has been consecrated for the purpose of something ‘holy,’ and actually used for this purpose, it cannot be deconsecrated. It remains consecrated, so that it may not be used for profane purposes, and it [an item] must be disposed of accordingly. However, not every ‘holy purpose’ would imply a consecration, and the halachah depends on further details. Furthremore, a temporary consecration, which is clearly limited by time, is not permanent.
Sources: See Shulchan Aruch, Orach Chaim 151-154.