The circuit with a reset button on it is a GFCI outlet, Ground Fault Circuit Interupter. It, along with all of the electrical in your house should NEVER smoke. PLEASE make sure that there is no residual heat behind it in the wall, I'm sure it was isolated but it is NOT good that it smoked. I don't want to alarm but please determine what else was on that circuit, eliminate all of the load and make sure the outlet and surrounding wall is cold to the touch and has no smoke smell. Electrical fires are one of the number one cause of household fires and I have heard many times someone saying they had a similar incident earlier in the day and then awoke to a fire. This is also the time to make a plug for working smoke detectors!! I don't mean to lecture, but I don't want to hear anyone has been hurt. Rant over, call an electrician to look at this outlet. The fact that you plugged in your tank should not have caused it to smoke unless something else is wrong electrically. Your circuits are limited to what they can provide and are rated above that for safety. Even so, add up all of the watts you are drawing with the tank, divide by 110 and you will have a rough idea of the amps your drawing. Most home circuits can provide 15 amps per outlet or up to 20 amps per circuit. I do have a dedicated outlet for my 150 though. Sorry to lecture, old job speaking.... Tony