The hot topic today in our industry today is lasers and new applications for using them. From welding and cutting, engraving and marking, to surface treatment and cleaning, lasers have become a very fast, precise tool. In fact, laser-based machine tools have grown into a $20 billion industry just in the last decade. This growth begs the question, what about safe use? Well, it all depends on the type of laser, the output energy, exposure time, and radiation wavelengths. These conditions are expressed in MPE (Maximum Permissible Exposure). Lasers are divided into classes, and each class has different hazards and risks involved, which must be addressed for safety reasons.
LASER CLASSES
CLASS 1 & CLASS 1M – These lasers cannot cause injury. They are specifically designed to prevent human access to laser radiation during operation. Some examples are: CD players, laser printers, bar code scanners, and DVD players.
CLASS 2 & CLASS 2M – These lasers are low power, less than 1mW, and are considered safe because the natural blink of an eye reflex will prevent any injury to the eye, but staring into these lasers could cause damage. Examples include laser pointers, some barcode scanners, and some light curtains.
CLASS 3R – Power range on class 3R is 1-5mW, considered safe for quick viewing, but can be dangerous if viewed directly or even when viewing a reflection from a smooth surface. Green laser pointers are an example of class 3R.
CLASS 3B – With a power range of 5-500mW, these laser beams can cause immediate skin and eye damage from a direct beam. Some examples are: laser light shows, industrial alignment and cutting beams, and even some 3D printers. Proper laser safety glasses should be worn if operating the machine or in the area which is called the NHZ (Nominal Hazard Zone).
CLASS 4 – Class 4 lasers are the most dangerous to the eyes and skin, and they also pose fire hazards. They are powerful, with a rating of 500mW or greater, and typically what we see in industrial lasers and medical devices. These lasers require proper PPE usage, and engineering controls must be in place, such as protective enclosures and interlocking systems that prevent workers from entering the NHZ.
It is important to note that businesses using class 3B or class 4 lasers must have a laser safety program in place. The safety program first starts with the election of an LSO (Laser Safety Officer). The LSO is responsible for the following:
- Managing the laser safety program
- Performing hazard evaluations
- Managing the laser equipment
- Control measures
- Worker training
- Accident investigations
- PPE recommendations
The safety program is a written set of guidelines and must be approved and managed by the LSO. Important parts of the safety program include standard operating procedures (SOPs), hazard assessments, employee training, maintenance policies, specific engineering controls, and signage.
The different types of required safety controls that must be put in place are:
Engineering Controls – this can include protective housing and gates, beam stops, interlocks (switches that automatically shut off the laser if the door or protective cover is opened), warning lights and alarms, and other barriers and screens that prevent or restrict access to dangerous laser beams.
Administrative Controls – these are the policies put in place by the company to reduce risks of injuries, such as proper training, SOPs, entry protocols, LSO assignment, warning signs, and incident investigations.
Personal Protective Equipment (PPE) – the least favorable of the controls and considered the last resort. Key PPE items are proper laser safety eyewear, flame-resistant clothing, and gloves.
Lasers can cause serious eye damage from direct view or reflection, causing burns to the retina. It is impossible to blink fast enough or turn away from a class 4 laser beam. So, it is important to wear proper safety glasses or goggles, and typical safety glasses are NOT the same as laser safety glasses. Laser safety glasses are selected by the specific laser application, wavelength, optical density (OD), and whether the user will have direct view or scattered/diffused view. It is very important to know all these elements before selecting the proper laser eye protection, as lasers can cause permanent eye damage. Here are the steps to consider when selecting proper eyewear.
- Laser Wavelength -measured in nanometers (nm), and in different colors: ultraviolet (100-400nm), visible ( 440-750nm), and infrared (750nm to 1mm), which is invisible.
- Laser Power– this determines the optical density that is required.
- Visible Light Transmission– this basically decides how dark the lens needs to be. It measures how much light will pass through and what that does to visibility. It is important to block harmful rays, but the user still needs to see.
Selecting the proper eyewear is not as simple as one might think and requires some research. There are excellent manufacturers out there that can advise you on what to choose when given the information on the laser.
With more industrial applications for lasers entering our industry, it is important to help the customer with proper PPE and other safety equipment needed. As always, they are buying this equipment from someone. Why not you?
