As promised I tested the smoke detectors when the boys were in their room with the fan on and the door shut and the lights off and them with their heads under the covers.

I think we nearly gave Sophie a heart attack.  She shook for about 30 minutes afterward.

The boys are good to go.  They both shot out of their room asking me to stop.

I am hoping this stops the fear of being able to sleep deeply and comfortably.  I suspect it was only a small piece, but absolutely not a reason any longer.

Praises for being able to actually show them this fear should not be keeping them from sleep.