The inside of a storage tank or pressure vessel is obviously a confined space, and before anyone is allowed to enter it, a systematic procedure should be followed. This chapter focuses on the events that result in accidents when people have to enter a confined space for a specific purpose. These fatal incidents happen either unknowingly or due to failure of quality checks. Many people have been killed inside tanks and other confined spaces. Sometimes they have entered without permission to do so or merely put their head inside an open manhole to inspect the inside. Sometimes entry was authorized, but not all of the hazardous material had been removed or it had leaked back in because isolation was poor. Sometimes hazardous material was deliberately introduced to carry out tests. Sometimes people have entered a confined space to rescue someone who has collapsed inside and have been overcome themselves. Various instances have also been discussed with examples of actual incidents like incomplete isolation, introduction of hazardous materials, weakness in protective material, etc. Confined spaces are usually entered through a manhole or similar opening that has to be unbolted before anyone can enter. This makes unauthorized entry difficult, though not impossible, because someone has to unbolt the entrance. This chapter also discusses the epidemics of unsafe entries and shares experiences gathered elsewhere. An important lesson that can be drawn is that the most effective way of overcoming the hazards of entry is to avoid the need for it. Various common reasons for entry, besides cleaning, and possible ways of avoiding the need are also highlighted.