This study will randomly assign emergency department patients seeking treatment for a headache to one of three groups. The first group will receive standard emergency care as determined by the treating physician, the second group will breathe high flow air by facemask for 15 minutes, and the third group will breathe high flow oxygen by face mask for 15 minutes. The patients will be questioned in the beginning of their treatment and at 2, 5, 10, 15 and 30 minutes after it's begun about the intensity of their headache and how much relief they are experiencing from their treatment. Concentration of carbon dioxide exhaled by patients will also be recorded at 0, 2, 5, 10, 15 and 30 minutes. After fifteen minutes, the patients in groups 2 and 3 will continue with standard emergency care, which can include any treatment their physician sees fit. Patients in all three groups will receive a stopwatch in the beginning of their emergency department visit and record the total extent of time their headache will take to resolve.

Thorough description provided in brief summary.

Inclusion Criteria:

• All patients who describe a painful sensation in the head as one of the primary reasons for their visit to the ED.

Exclusion Criteria:

• patients who need immediate oxygen after triage: Recent fire or carbon monoxide exposure_______ O2 saturation 94% or less on room air on triage vitals ______ patient arrives on supplemental oxygen_______ patient reports shortness of breath_______
• patients in whom 100% oxygen is contraindicated, potentially undesirable, or controversial: history of COPD_______ possible cardiac ischemia (mouth / jaw / neck / shoulder / chest / abdomen pain or pressure)_______ possible stroke (new focal weakness or numbness, speech, hearing or vision deficit, bowel or bladder incontinence or retention)_____
• patients unable to tolerate the gas treatment: patient not able to tolerate a face mask_______ patient requests immediate treatment with another preferred therapeutic agent_______
• treating physician or nurse request to discontinue the study at any point_______
• patients who have diminished decision-making capacity history of mental retardation or pervasive developmental disorder_______ patient not awake and alert_______ patient not oriented to self, month and year, and current location_______ patient unwilling or unable to fully participate in the research associate interview and consent process_______
• patients who are at risk for intracranial hemorrhage history of intracranial aneurythm, hemorrhage, surgery, or tumor_______ current headache began after trauma_______ current headache began after using elicit drugs_______
• patients who are at high risk for intracranial infection fever > 100.4 F on triage vitals_______ complaining of recent onset neck stiffness_______
• patients who are at high risk for extracranial head pathology ear pain or drainage_______ tooth or gum pain_______ headache localized to a skin lesion on the head______
• patient is potentially critically ill active bleeding from any source_______ heart rate <60 or >130 on triage vitals_______ systolic blood pressure <90 or >180 on triage vitals_______ respiratory rate < 10 or >30 on triage vitals_______
• patient is younger than 21_______
• patients who know or suspect they are pregnant _____

Limited number of subjects due to difficulty with recruitment