People have been dumping polystyrene wrapping in with the cardboard and paper and that contaminates the load - either it can't be used or it has to be sorted and that takes time and money which may make recycling uneconomic.

The ACT government has decided to try a new scheme to make it harder to dump the polystyrene which wraps a lot of the white goods like fridges, televisions and washing machines it expects people to get on December 25.

At the Tuggeranong Recycling Drop Off Centre, there'll now be a small slot which will take cardboard easily but which will be too small for the big polystyrene coverings. In the past, a big hole has been there to push material through - including unwanted polystyrene.

"When recycling becomes too contaminated, materials may not be able to be recycled," ACT recycling manager, Michael Trushell, said.

Mr Trushell said that polystyrene and loose plastic wrapping was "a major contaminant" because it was often left inside the cardboard box.

"We ask users of the facility to separate any polystyrene and loose plastic wrapping materials to keep them out of the recycling stream," Mr Trushell said.

"We have also changed the design of the paper and cardboard cage from a large sliding gate to a smaller slot, aimed at ensuring boxes are emptied and flattened before placing them in the cage. This will help reduce the amount of polystyrene blocks making their way into our recycling stream."

The trial will run until the end of January when it will be assessed to see if it has worked.