One of the more dangerous aspects of a spiral staircase is the fact that they have an open-back construction. This means that there is space between each stair, which could result in someone falling through the staircase. While that space is one of the things that makes a spiral staircase attractive, it also can be dangerous.
While it is important to childproof all potentially dangerous areas in your home, this is especially true of a spiral staircase. Install a baby gate at the foot of the stairs so that the child cannot climb up them. Protect the child against climbing into the staircase from between the lower stairs by placing protective barriers inside them. The manufacturer of your spiral staircase likely sells barriers that fit the space. Install these all the way up the staircase if you have a small child who will be using the staircase so that she cannot fall through the stairs.
Make your spiral staircase safer when you design it. By limiting the amount of space between each stair, the backless design of the staircase becomes safer. For example, if the stairs are shallow, with only a few inches of space between each one, it becomes much more difficult for a person to slip and become injured by falling through the space.
One way in which a spiral staircase is actually safer than a traditional staircase is in all of the areas a person has to hold onto. A person can hold onto the railing on the outer area of the staircase while walking up the stairs. The pole in the center of the staircase can also help a person balance while walking up the stairs.