“There are three basic types of triage. Primary triage is the first triage of patients into the medical system (it may occur prehospital), at which point patients are assigned an acuity level based on the severity of their illness/disease. Secondary triage is the reevaluation of the patient’s condition after initial medical care… This may occur at the hospital following EMS interventions or after initial interventions in the ED [Emergency Department]. Tertiary triage is the reevaluation of the patients’ response to treatment after further interventions and is ongoing during their hospital stay. This is the least practiced and least well-defined type of triage. “Historically, triage has involved four levels of priority for traumatic injuries: (1) Green - delayed treatment - has minor injuries or illness and should not pose a threat to life or limb. (2) Yellow - intermediate - has injuries or illness that may result in death or disability but pose no immediate threat to life or limb. (3) Red - critical - has injuries or illness that will result in death within the hour unless interventions occur. (4) Black - expectant or deceased - is expected to die because of severity of illness or injuries or has died. “An experienced health care provider should be involved in any decision to classify a patient as “black” during a disaster…all such patients should have access to palliative care (analgesia, sedation, physical and behavioral cares) to the extent possible under the circumstances. Expectant patients should be reassessed regularly for comfort, for improvements in their situation, or in case resources become available unexpectedly. “Studies have shown that experienced health care providers are generally very accurate at assigning triage levels in the ED on a daily basis,70 though there are no studies to determine to what degree this is true in disasters”. (AHRQ/HHS, Mass Medical Care…, p. 71)