I remember years ago, when I was just 8 years old, my brother and I had a nice little bunk bed. Our parents had purchased it for us with the intentions of keeping the bunk bed separate into two twin beds but with much convincing, our parents finally gave it and built it into a stackable bunk bed. Of course, being the younger brother that I am, I got the lower bunk. My brother was never really a calm sleep. He had a habit of moving around quite a bit while sleeping and once in awhile talking in his sleep and making random movements. While this would not normally be a problem had it been the lower bunk, this got my parents somewhat worried.
I remember the day that my brother fell off the top bunk. Fortunately, he was not injured, but he was pretty shook by the fact that he had just tumbled roughly six or seven feet from the top bunk. My brother avoided a potentially dangerous fall that could have seriously injured him, like the 500,000 children and adults who become injured and sometimes die from bunk bed related accidents. Children and adults alike are at their most vulnerable stage when they are asleep. You or your children may not know exactly what kind of movements they are making while sleeping. Sleepwalking is actually quite common in children and adults. While my brother was lucky enough to not get injured, this is something that should not be ignored.
Now at an older age, I cannot stress this enough to all parents. Yes, kids love bunk beds, and I realize that they save space and money, but please consider all safety standards before purchasing one. Common safety rules such as no jumping or standing on the top bunk should be strictly enforced. Similarly, place your kids bunk bed where your children will have enough headroom to sit up and easily climb in and out of bed. Placing your bed under a ceiling fan or light fixture is also not the best idea. Pay attention to details! Like everything else, it is better safe than sorry.