Electricity in a house is (usually!) installed by licensed electricians and inspected after installation, ditto gas and heating devices.<p>If you stay in someone else&#x27;s apartment and it does not have a CO alarm and a stove that may or may not vent into the apartment then you should at a minimum sleep with a window open.<p>Tree-swings are not usually installed by licensed engineers, they are typically installed by people with a tree with a suitable profile, a rope and an old tire, any of which may fail at unpredictable times, but most likely when being used (and even more likely: when being used by an adult).