The Food and Drug Administration (FDA) has classified all lasers, both medical and non-medical, into four categories. Lasers classified as "Class IV" (or "Class 4) emit more than one watt of power. These devices are intended for use by trained professionals who will be responsible for the proper application of the device.
Lasers that fall into this category are used in surgery because of their high level of precision. They can cut through bone, tissue, and other material with little or no pain for the patient. However, they are also the most expensive because of their requirement for a surgeon to perform operations using them.
Medical lasers fall into three main classes: Class I, Class II, and Class III.
Lasers are classified into seven categories based on the potential for the beam to inflict injury. The categorization and hence the hazard are determined by the wavelength, power, energy, and pulse characteristics. The laser's class can be used to assist determine what safety controls are necessary while utilizing the laser. Class I lasers are visible to the human eye and therefore require protective eyewear. These lasers are typically used for fine work such as welding or cutting materials that do not significantly scatter light. They are also used in medical applications to view inside bodies without opening them up surgically. Class II lasers are close-proximity lasers that can cause skin burns and eye damage if they hit the body directly. People who work with these lasers need protection from both visible and infrared light. They usually have a red filter over the lens of their eye protectors. Class III lasers are far-field lasers that cannot injure anyone within 20 feet of their source. They require permanent shielding that prevents any part of the person working with the laser from coming in contact with its beam. Personnel must always wear protective clothing (goggles or a hat) when around this type of laser for complete protection.
Class IV lasers are intermediate-range lasers that can cause serious injury if they hit a body part with enough force. These lasers should only be operated by trained personnel in controlled environments. Protective equipment is required when working with this type of laser. It consists of a face mask for those working near the beam and goggles for those working farther away.
There are four major kinds of visible-beam consumer lasers. Each of the following classes is explained in further depth below: Class 2, Class 3R, Class 3B, and Class 4. The first two classes are quite safe for ocular exposure, whereas the latter two are risky. The graphic below depicts how the risk of eye harm grows as the laser's power increases.
The output of a laser can be expressed in milliwatts (mW), watts (W), or lumens. A laser beam in air at room temperature has a maximum intensity of about 1 W/cm2. Laser pointers, which are designed to produce high-intensity beams over large areas, typically operate at powers of 100 mW to 5 W. Smaller laser diodes used in portable devices reach high temperatures and therefore require safety precautions even when not operating them. These devices usually have power levels of less than 1 W. Larger laser diodes used in industrial applications are often operated with powers of up to 100 W or more.
Lasers can cause injury to humans who are exposed to their beams. This happens when the light strikes your retina, which is made up of millions of photoreceptors that detect light signals from the outside world. When exposed to intense beams of laser light, these receptors can be damaged, resulting in blindness. Other serious effects include damage to the heart, lungs, and blood vessels due to heat buildup in these organs during laser operation.
What exactly is a Class 4 Laser? Exposure to Class 4 lasers is dangerous to the eyes. They may also burn flesh and materials at close range, particularly dark and/or lightweight materials. They must be used with considerable caution. The risk of injury increases with higher power levels.
Class 4 lasers are typically operated by an authorized technician within a controlled environment. The laser can deliver a beam of up to 100 m (330 ft) in length and 1 m (3 3–4 ft) in diameter. Power ranges vary but most operate between 10 watts and 100 watts. Some reach powers of up to 500 watts for very small periods of time.
Lasers can be used for many different applications including material processing, medicine, science, and technology. They can also be used as weapons. Lasers work by using the properties of light to produce effects in matter. This process allows them to cut through materials as if they were thin water.
The effect of light on matter can be useful for cutting materials, seeing into caves, or capturing images. The same effect can be harmful if not used properly. Lasers have potential to cause serious eye damage if not handled properly.
People who operate class 4 lasers should always wear protective eyewear when exposed to their beams. This includes goggles or a helmet with transparent lenses.