A look inside a more modern Dezac Breathe Easy ioniser.

I dug this old ioniser out because I was sure it had a nearly identical PCB to the older version I'd taken apart.
It does, but this one had been in use for some time. When I bought it on ebay as used it was making hissing noises inside but producing no detectable output into the surrounding air.
The PCB is discoloured where tracking has occurred between the high voltage circuitry and the inappropriately close mains ground referenced end of the multiplier.
You can see where the needles have been discharging directly to the adjacent diode leads and there is a strange crusty corrosion on them that has clearly made matters worse.
The hissing noise inside was the high voltage tracking directly across to the low voltage area and rendering the ioniser useless.