B737 Undifferentiated or Other Model
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 216.63; Flight Crew Type 6653.95
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Aircraft Equipment Problem Dissipated; General Physical Injury / Incapacitation
Procedure; Aircraft
During preflight action external inspection; First Officer was exposed to hydraulic fluid which was leaking in wheel well area. Fluid leak became mist when the air from packs came in contact with the leak. Prior to leaving the flight deck; the hydraulic systems were pressurized due to control movement from outside sources. After exposure to First Officer's eyes; [Chief Pilot] was contacted which lead to medical attention per [Chief Pilot] checklist procedures.
During the preflight exterior inspection; I was sprayed in the eyes with a mist of hydraulic fluid.  Prior to exterior inspection; hydraulic system was pressurized to stop control column movements. APU was running and providing conditioned air. As I approached the wheel well area; I thought I noticed an unusual smell. When I stood up into wheel well; I was sprayed in the face with a fine mist. My eyes began to burn. I warned one of the nearby crew chiefs to stay clear of the wheel well. He directed me to the nearest eye wash station. On the way to the eye wash; I went to cockpit; notified Captain we had a leak. Depressurized the two electric hydraulic pumps. Told him I was going to the eye wash. Maintenance's subsequent inspection found a loose hydraulic fitting near where the conditioned air is exhausted. The exhausted air was turning the leaking hydraulic fluid into a fine spray.
B737 flight crew reported that during preflight inspection; leaking hydraulic fluid came in contact with Air Conditioning Pack exhaust air; becoming mist which contaminated the eyes of the First Officer; requiring medical attention.