Which of the following describes a Class 4 laser?

A Class 4 laser is one that can indeed cause significant harm to both the eyes and skin upon direct exposure. This classification of laser is noted for its high output power, which means that even brief exposure can lead to severe injury, including permanent blindness or burns.

Class 4 lasers are often used in a variety of applications, such as industrial cutting and medical procedures, due to their ability to produce high energy levels. Users must be trained and use protective measures to ensure safety when operating or being near these lasers.

The other options either suggest a lack of risk associated with Class 4 lasers or incorrectly categorize their use. Such lasers cannot be considered safe for public use without appropriate safety protocols and protective equipment in place.