Despite safety concerns, there are many low-cost systems that use glass laser tubes, which are powered by high-voltage direct current and cooled with water. Basically, cool water is circulated around the glass laser to keep it from overheating. In the case of water leakage, damage to the glass laser tube, or direct contact with any of the high-voltage elements, there is a serious risk of electric shock. With voltages in excess of 25,000 V and currents ranging from 30 to 150 mA, an electrical shock can be lethal. Careful consideration should be taken before purchasing a laser system built with high-voltage glass lasers in any environment, but particularly in schools. The safe choice is an air-cooled laser system with a low-voltage power supply.
This information originally appears in a Universal Laser System blog post.
—Thea Sander, Universal Laser Systems