(b)(4).Method: the complaint 900mr755 reusable heater wire was returned to fisher & paykel healthcare (f&p) where it was visually inspected and analysed.In addition, further testing was conducted to simulate the reported event using samples of the 900mr755 reusable heater wire.Results: visual inspection of the returned 900mr755 reusable heater wire showed blackened marks across the heater wire and the heater wire module.The returned device was further analysed using an electron microscope and scanning electron microscope analysis.Bubbles were observed within the wall section of the connector to the breathing circuit, which indicated resin degradation due to rapid heating.It was further observed that the chamber socket area was unaffected, and the charring was confined to one section.From the analysis, it was determined that the observed damage was likely due to the presence of external flammable materials.Further testing was conducted to confirm this hypothesis using a sample of the 900mr755 reusable heater wire.A fire was unable to be produced without the presence of external flammable materials.Conclusion: based on these findings, it is concluded that within the prescribed operating conditions, a fire could not be produced.We are unable to confirm the cause of the reported event.However, the observed damage was most likely due to the presence of external flammable materials during use.All heater wires are tested during production.Any heater wire that fails will be rejected and disposed of.The subject device would have met the required specifications at the time of release.Our user instructions for the mr850 respiratory humidifier state: · check accessories for damage before use and replace if damaged.· remove any sources of ignition, such as cigarettes, an open flame, or materials which burn or ignite easily at high oxygen concentrations.
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