According to the Medterms website, mucus is "a thick slippery fluid produced by the membranes lining certain organs such as the nose, mouth, throat..." Mucus in the chest and throat can be caused by a number of things. Most commonly, it is a symptom of a respiratory ailment such as a common cold or flu. Eucalyptus oil is an "essential oil" used in antiseptics and cough drops. You can use it to make a steamer that will help clear out mucus in the chest and throat and allow you to breathe more easily.
Fill a tea kettle with tap water. Place it on your stovetop and bring the water to a boil.
Fill a medium-sized pan with the boiling water. Add a drop or two of eucalyptus oil to the water.
Place your face above the pan---close enough so you can inhale the steam, but not so close that you get scalded.
Drape a towel over your head and the metal pan, forming a "tent" to help hold the steam and eucalyptus vapours in. Close your mouth and breathe in deeply through your nose for five minutes.
Blow your nose with facial tissues as the congestion becomes thin and clears out. You'll cough up mucus from your chest as well. Repeat this twice a day as needed.
If the mucus is accompanied by a prolonged fever above 38.3 degrees Celsius, chest pain, a sore throat, severe hoarseness, intense pain around eyes or in an ear, difficulty breathing or a cough with yellow or green mucus or blood, seek professional medical help.