This will be brief. I know language changes, but there is one set of words consistently confused with each other: Damp and dampen.
Examples: Dampen the market rise, dampen the excitement, dampen the fluctuations in defect rates.
The word is damp! Oscillations are damped, not dampened!
Does your fireplace have a damper, or dampener? Probably a device to damp the flow of oxygen, that also closes the chimney altogether. It's possible that you also have a dampener if there is a device to spray water on a fire that's out of control.
There's an odd logic to word substitutions like this. Rain does tend to dampen spirits at a picnic, but most of the time when people use the word, there's no water involved.