You can make a fragrant freshener based on eucalyptus with the following ingredients.
7oz/200g eucalyptus leaves
1 3/4 pints/1 litre of vinegar
Marinade the eucalyptus leaves in the vinegar for 2 weeks, then strain off the leaves and discard them. Store the freshener in a screw-top jar. To use, place a small amount of the liquid in shallow bowls close to central heating radiators