You can use a Palo Santo stick or Palo Santo Atmosphere Mist to smudge areas or people, you can do this by gently circling around a person, object or space until you feel it is clear. However for thoroughly cleansing a space of very negative energy, such as after an event, an argument or any such stuck energy you can feel you will need to burn at least 2-3 sticks together - if the place is small to medium size. For the cleansing to be well done, the room must be completely fogged - so you cannot breath and your eyes burn. As this is quite a powerful cleansing, the room should be empty for at least three hours after doing this.
Using Crystals To Cleanse Energy in a Room
I often work with crystals for their energy balancing vibrational qualities too. Crystals have a vibration which is constant - this has been scientifically proven (ever wondered why silicon chips are used inside your computer? or why quartz was used inside watches? you can read about this anywhere on the internet). You, a highly complex electromagnetic field, can align with many different types of crystal - which all have different vibrational qualities - to balance or raise your own vibration which is constantly in flux.
Usually I use three protective Obsidian pyramids - a feng shui practitioners favourite - to absorb any negative energy. Then a high vibration Himalayan 'Nirvana' quartz to raise the frequency in the room. Combined with the Palo Santo this will amplify the positive intension to purify the space and send any stuck energy back to source with love.