Which of the following best defines confined spaces?

The definition of confined spaces primarily revolves around the physical characteristics that allow for human entry and work, while also encompassing certain safety considerations. A confined space is typically characterized by being large enough for an individual to enter and perform various tasks, but it is not designed for continuous human occupancy. This means that while a person can access the space to conduct specific work, it may not have adequate ventilation or may contain other hazards that could affect safety.

In contrast to the other options, which focus on different aspects like the presence of special tools, ongoing ventilation, or intentional design for occupancy, the correct answer highlights the essential feature of these spaces: they must provide enough room for a person to enter and work effectively, irrespective of the tools or ventilation conditions present. Therefore, recognizing that the ability to engage in tasks within the confines of the space is the primary defining factor allows for an appropriate understanding of the nature and safety implications associated with confined spaces.