What is the takeoff measurement of a 4& long radius piping ell?
My apologies, Mr. Perfesser, meant to give you a thumbs up. It won't let me retract my vote :(
The battery is installed as a back-up if the power goes up. The 9V battery is not a rechargeable and needs to be replaced. Turn off the AC power to the detector at the breaker, pull the old battery, replace with new, turn power back on.
Depends where you live.call your local fire department and talk to someone in code enforcement
