Teardown of an Ambi Pur 3volution three scent air freshener.

This is a look at the insides and circuitry of a UK air freshener (aroma plug) that cycles round three different bottles of aroma chemicals in sequence.
It was held shut by heat-staked plastic rivets as is often the case with the high profile brands. It's probably a cost saving thing, but also acts as a deterrent to people opening them up! Oh well, nothing a drill won't fix.
The circuitry works on half wave rectified mains and a simple resistive dropper that powers a COB (chip on board) blob that switches the individual heater resistors across the half wave rectified mains supply with three little TO92 devices that turned out to be high voltage transistors. Each resistor has a value of 17,000 ohms meaning that they will pass about 14mA on a 240V supply dissipating around 1.5W because they are only powered on one half of the mains cycle. There's a level setting switch which probably just cycles each resistor on and off to vary the aroma level. The chip also controls three LEDs independently of the resistors to show which aroma bottle is active at any given time.
The idea is that you get a continuously changing aroma, but the three tend to be quite similar and it's not really noticeable.
There are knock-off refills available in pound stores that are usually a tight fit and quite weak in the aroma department. But they can be refilled with things like lavender, citrus and peppermint oils to make the smells more interesting and noticeable.