Which laser class can be safely used without protective eyewear under controlled conditions?

Class 1 lasers are designated as safe to use without protective eyewear in controlled settings because they emit light levels that are not hazardous under normal operating conditions. This means that even if a person directly stares into the beam, the output is below the threshold that would pose a risk of damage to the eye.

In contrast, Class 2 lasers, while generally considered safe for brief exposure (due to the natural aversion response of blinking), still necessitate caution since prolonged exposure can be harmful. Class 3 lasers can be hazardous, with potential risks depending on their specific subclass, and protective eyewear is typically required. Class 4 lasers are the most dangerous, capable of causing immediate eye injury and even posing fire hazards, thus requiring both protective eyewear and strict safety protocols.

Therefore, Class 1 lasers stand out as the only category that allows for safe operation without the need for protective eyewear in controlled environments.