Additional Manufacturer Narrative · 1
FIRE CAN ONLY START WHEN THREE ELEMENTS ARE PRESENT, FUEL (DRY CIRCUIT WICK), OXYGEN (CONCENTRATED O2 INSIDE CIRCUIT), AND HEAT SOURCE (SPARK FROM ELECTRICITY). BASED ON INTERNAL TESTING AND THE CUSTOMER'S DESCRIPTION OF THE INCIDENT, IT APPEARS THAT MULTIPLE OPERATING AND HANDLING CONDITIONS WORKING TOGETHER CONTRIBUTED TO THE EVENT. ANY ONE OR ANY OTHER COMBINATION OF THESE EVENTS COULD NOT CAUSE THE FAILURE. FIRST, THE CIRCUIT WAS DRY, AS INDICATED BY THE CUSTOMER REPORT OF SIX HOURS OF USE WITHOUT REWETTING THE CIRCUIT. SECOND, THE WIRES WERE DAMAGED FROM AN EXTERNAL IMPACT, MOST LIKELY OCCURRING DURING PT MOVEMENT. BECAUSE THE CIRCUIT WORKED CONTINUOUSLY AS DESIGNED FOR OVER SIX HOURS PRIOR TO THE EVENT AND THAT THE DAMAGE TO TWO SEPARATE WIRES WAS IN THE EXACT SAME LOCATION, IT DOES NOT APPEAR THAT THE WIRES WERE DAMAGED DURING THE FIRST SIX HOURS OF OPERATION. BASED ON THE CONDITION OF THE CONTROLLER, DAMAGE OCCURS TO THESE PRODUCTS WHILE IN USE. IN ADDITION, THE RIGHT TWO WIRES HAD TO BE DAMAGED IN THE IMPACT FOR THE EXPOSED AREAS TO HAVE THE CORRECT POTENTIAL TO CREATE A SPARK. FINALLY, DURING PT USE THE CIRCUIT WAS FILLED WITH 80% O2 CULMINATING IN A RARE SITUATION RESULTING IN FIRE FROM THE MOMENTARY WIRE SHORT DURING OXYGEN FEED. THE CONTROLLER FUSE DID NOT FAIL BECAUSE THE DAMAGED WIRE CONTACT WAS INTERMITTENT (<1/10 OF A SECOND). THE SPARK FROM THE INTERMITTENT CONTACT WAS EXACERBATED BY THE OXYGEN RICH ENVIRONMENT CREATING THE INTERMITTENT FLAME OBSERVED BY THE USER. REIMPLEMENTATION OF IRRADIATED WIRE WILL INCREASE THE CUT THROUGH RESISTANCE OF THE WIRE; THEREFORE, FURTHER REDUCING THE POSSIBILITY OF THIS SITUATION RECURRING.