I actually volunteered in the Harborview Burn Unit when I was in high school for about two years. If you want some up close and personal exposure, you will sure get it there. The friend of the last poster is right- it is intense. As an example, a volunteer during my time threw up on the first day and never returned. For myself, however, it was a huge driving force in sending me down a medical career path- here I am now applying to medical school. I still talk about many of my experiences there.
As far as the exposure went, I assisted with wound care very frequently, which was very emotionally draining at times. I can remember a couple times when patients with extremely severe burns on all sorts of pain meds were screaming in agony. Words cannot describe what heat can do to human flesh. ...The wound care itself involved changing the wraps, cleaning, etc. There wasn't much in the way of clerical work to be done, but sometimes I would be sent on errands (blood bank, etc.).
Look around though at Harborview. It is a great facility, and the medical staff is outstanding. Patients come in from Alaska, Idaho, Wyoming, and Montana for the ED and Burn Unit, and probably other highly specialized departments. There is a lot to see, so go with whatever interests you. If the Burn Unit sounds like something you would enjoy, I recommend it.