The old police station building in Christchurch will be reduced to rubble this afternoon.

LIVE STREAM: Watch the implosion live from 5pm

A controlled implosion is being used to bring the building down, at 5pm.

An exclusion zone has been set up and security arrangements are in place to make sure no-one gets hurt.

Demolition company Ceres NZ spokesman Bernie de Vere said though it takes some time to plan an implosion it's the best option in bringing down a building in the CBD as it won't interfere with traffic.

"Durham St is quite a busy road, and by taking this building down, it will be open to the public tomorrow. Whereas if we were doing a cut and crane exercise it would've taken months."

He said the implosion shouldn't cause any more dust than a conventional demolition would but precautions should still be taken.

"We'd advise anyone local to turn off air conditioning, keep windows closed, and the dust will settle very quickly."