Laser Safety Glasses Frequently Asked Questions
Laser safety starts with knowledge. Without it, blindness can happen in the blink of an eye. Lasers span distances at the speed of light, which, according to physics, is the fastest speed possible. There will be no warning before a laser beam does its damage. One instant, you are fine, and the next, you aren’t.
Besides their near instantaneous speed, laser light is collimated. That is, their rays of light are nearly parallel. This means the energy intensity of a beam diminishes little with distance. Depending on the laser, its beam may spread out by only a tenth of an inch after traveling ten feet.
This is quite different from ordinary light, which diminishes in intensity with the square of its distance. For example, its intensity diminishes by a factor of four when its travel distance is doubled. This is why a one watt laser can blind you from tens of feet away, while a 100 watt LED light won’t.
Eye exposure to a laser does not necessarily cause blindness, however. Lasers in the class 1 & 2 categories are generally considered safe, unless you deliberately stare into the beam for lengthy periods. This is especially true of class 2, which is safe if your blink reflex causes you to look away. Class 3B & 4 lasers will damage the eye and potentially cause blindness if the laser’s wavelength allows it to penetrate past your cornea and lens. Visible light and short wavelength infrared do this.
In terms of laser safety, the above facts mean that your eye health hinges on knowledge and the willingness to act on it so that you never make that one mistake that could cost you your vision. Here are seven frequently asked questions and answers about laser safety and laser safety glasses that might save your vision:
When Should I Wear Laser Safety Glasses?
Wear laser safety glasses when using or when you are with others using class 3B and class 4 lasers. Class 3B lasers have sufficient power to damage the eye when viewing the beam directly, even for a brief instant. Beam reflections off specular (shiny, mirror-like) surfaces are also harmful, while diffuse reflections from coarse, rough, or any non-shiny surface, such as concrete, are safe. With class 4 lasers, looking at any kind of reflection including diffuse reflections will injure your eyes. That means looking at the spot where the beam hits the target is harmful.
Of course, you should wear laser safety glasses whenever the rules or protocol require
it, such as when you are in an area with signs requiring their use.
How Long Will My Laser Safety Eyewear Last?
This depends on the wear and tear process. The more effort in taking proper care of the glasses, the longer they will last. Avoid scratching the lenses by not dropping or placing them lens-down on any hard or abrasive surfaces. Do not place them in areas full of dust, dirt, or grit.
To avoid accidentally dropping your glasses, hold them carefully and put them on deliberately — not while multitasking. Never leave them unattended in areas where they may be knocked to the floor, sat on, or stepped on. Keep them clean by washing with water and a non-alkali/acidic soap or detergent. Use a lint free cloth.
Note that environmental conditions can degrade your safety eyewear. Avoid keeping them in places that see extreme heat, such as the inside of your car on a hot day, or in a hot garage or attic.
Are There Laser Safety Glasses That Protect Against All Types of Lasers?
No. Laser safety eyewear will filter out a wavelength of light specific to the laser used. For example, a blue laser will require different safety glasses than that required by a red laser. Some laser safety glasses are designed to filter out multiple wavelengths, which provide protection from the corresponding types of lasers. However, glasses that protect against all lasers (all wavelengths) would filter out all light. This means no light reaches your eyes, making it impossible to see.
Is Laser Eye Protection Needed When No Laser Beam Is Visible?
Inability to see a beam does not mean you are safe from laser exposure. The laser beam may be hidden from your line of sight. Changing your position may expose you to the beam or a reflection. In addition, some lasers are invisible, such as ultraviolet and infrared. Always follow established safety protocol about when to wear laser eye protection and when it is safe to remove them.
What Are the Signs of Worn or Damaged Laser Safety Eyewear?
Look for signs of lens damage such as scratches, cracks, discoloration, gouges, or holes. Never wear laser safety glasses with damaged frames or straps, even if the lenses are in good condition. You can not count on them to reliably hold the lenses in place.
If the wavelength and optical density labeling on the glasses is worn off or is otherwise missing, replace the labeling or discard the glasses. Even if you know this information, someone else won’t and may use the glasses with lasers that they won’t protect against. Of course, one should never use laser safety eyewear without knowing the type of laser light it’s supposed to filter out.
Will Laser Safety Glasses Protect Against Impact?
They are only meant as protection against laser light. The lenses of some laser safety glasses are made of polycarbonate. Although this plastic is very tough, don’t assume the glasses are impact resistant if the labeling makes no mention of this. If you require this kind of protection, wear suitably sized impact resistant goggles over your laser safety glasses.
How Do I Select the Right Laser Safety Eyewear?
The optical density and wavelength marking on your glasses must be correct for the laser you are using. The optical density indicates the beam energy intensity that the glasses can safely attenuate. If the wavelength does not match that of your laser, the beam will pass through the glasses with little if any attenuation. Getting either of these two requirements wrong can cause injury and possibly blindness.
Talk to your laser safety officer and contact us at Phillips Safety Products for information on this and to obtain the right pair of laser safety glasses.