another thing you'll want to protect your family from is carbon monoxide which is a byproduct of fire gas burning appliances like water heater stoves furnaces and fireplaces give off carbon monoxide which is supposed to be vented completely out of your home now this gas is a deadly poison so when it builds up in a home the results are tragic and because it's colorless and odorless a carbon monoxide detector is the only way to know if you have a problem now you can find these things as standalone units that can just plug right into the wall or just sit it on a tabletop but most manufacturers also offer them in a combination device that detects smoke as well as carbon monoxide that way there's one less battery to remember to replace a speaking of that all of these devices need batteries either as a backup or for primary power but they won't protect you that battery is dead so change them every six months now the detectors won't last forever either so write the date when you buy the unit on the back of these that way you'll see exactly how old they are and when you need to replace the unit every time you change the batteries