Lasers are high-energy radiations that are extensively used in labs and industries in the modern economy.
Their fields of application include various medical laser procedures, industrial laser cutters, and devices like CD/DVD players, laser printers, barcode scanners, laser pointers, etc.
Despite being really useful, lasers can be quite dangerous when used incorrectly and pose a severe risk of injury to your eyes.
Laser Safety is about designing and using lasers safely to minimize the chances of laser accidents.
This article discusses lasers, hazards posed by different types of lasers, laser safety standards mandated by Occupational Safety and Health Administration (OSHA), and general safety rules for all types of laser applications.
What is a laser?
LASER is an acronym for “light amplification by the stimulated emission of radiations”.
It is a high-energy beam of light that is focused into a tight spot using optical instruments like lenses and mirrors.
Different types of lasers have been developed over time, with different wavelengths covering the electromagnetic spectrum’s visible, infrared, and ultra-violet regions.
Depending upon their wavelengths, various types of lasers are available in the market.
| Laser (type) | Radiation Type | Wavelength (nm) |
|---|---|---|
| Carbon dioxide (gas laser) | Infrared | 9,300-10,600 |
| Nd: YAG (solid-state laser) | Infrared | 1,064 |
| Fiber (solid-state laser) | Infrared | 780-2200 |
| Diode (solid-state laser) | Visible (red/blue/green) | 450-950 |
| Argon (gas laser) | Visible (blue/green) | 488-514 |
| Krypton KPT 532 (gas laser) | Visible (green) | 532 |
| Ruby (solid-state laser) | Visible (red) | 694 |
| Rhodamine 6G Dye (Tunable – dye laser) | Visible (green/red) | 570-650 |
Various types of lasers
Laser Safety Standards
Laser safety standards provide guidelines for the proper use of laser equipment in different occupational environments.
It also details what to do in case of any accidents.
These safety standards differ from one region to another, and the standards pertaining to your region must be followed.
In Australia, the safety standards for laser operations are governed by AS/NZS 2211(Laser Safety) and AS/NZS 4173 (Guide to the Safe Use of Lasers in Healthcare).
Laser safety in European countries is governed by the International Electrotechnical Commission (IEC) and European Standards (EN) provided in the EN 207 and IEC 60825 documents.
For the United States of America, the Occupational Safety and Health Administration (OSHA) has determined the American National Standard (ANSI Z136) as the guidelines for laser safety.
Classification of Lasers according to Risk of Injury
There are two classification systems of lasers, the ‘old system’ and the ‘revised system’.
The International Electrotechnical Commission (IEC) introduced the revised system in 2002.
American National Standards Institute (ANSI) has incorporated the revised system in their ANSI Z136 standards, and therefore, we will be discussing the “revised system” of laser classification.
Each laser class has a specific warning label that should be installed on the device and in the area where these lasers are being used.
| Class | Laser Hazard | Application |
|---|---|---|
| Class 1 | Not harmful under normal operating conditions | Laser printers |
| Class 1M | Safe to look at with naked eye, but can be harmful if viewed through an optical enhancer | Telecommunication systems |
| Class 2 | <1mW, continuous wave visible laser that can be harmful when looked at for prolonged time | Bar code scanners |
| Class 2M | Blink reflex prevents serious damage, but can be harmful if viewed through an optical enhancer | Optical level used in constructions |
| Class 3R | 1-5mW, visible laser that can cause damage if comes in direct contact with the eyes. | High power laser pointers |
| Class 3B | 5-500mW, continuous wave that can cause instant eye damage faster than blink reflex. | Laser light show projectors |
| Class 4 | >500mW, continuous wave that can cause severe eye damage and skin burns | Industrial lasers |
Laser classification table
Class 1 Lasers
A Class 1 laser is not harmful under normal operating conditions, even when looked at by the naked eye.
Some common examples of class 1 laser equipment are laser printers and CD/DVD players.
Class 1M Lasers
Similar to class 1 laser, class 1M lasers are not harmful when looked upon by the naked eye.
However, the Maximum Permissible Exposure (MPE) of these lasers can be exceeded when looked at through an optical enhancer like a magnifying glass, microscope, etc.
These lasers are generally used in fiber optic communication systems.
Class 2 Lasers
A class 2 laser is a 1 mW continuous-wave visible light laser that can be dangerous when looked upon for a prolonged time.
These lasers are considered safe as the damage to the eye can be prevented by the blink reflex of eyes to visible bright light.
A bar code reader is one of the most commonly used examples of class 2 lasers.
Class 2M Lasers
Similar to class 2 lasers, these lasers are considered harmless, and the blink reflex can prevent damage to the eye.
Class 2M lasers are dangerous only when looked at through a magnifying glass or other optical enhancers.
These lasers are most popularly used in leveling and orientation instruments.
Class 3R Lasers
A visible class 3R laser can have a continuous-wave laser power of up to 5 mW which can go higher in the case of pulsed lasers.
Depending upon the type of laser beam and its power, these lasers can cause damage when staring directly at the laser with the naked eye.
But the risk of damage with class 3R lasers is very low, and serious injuries can be prevented by blink reflex.
These lasers are commonly used in high-power laser pointers.
Class 3B Lasers
A visible class 3B laser has a laser power ranging between 5 mW and 500 mW.
These lasers can cause immediate damage to the eye when looked at by the naked eye.
Therefore proper eye protection is necessary when using these lasers.
The reflected beams of these lasers are generally not harmful, but staring at the laser dot on a surface from close range should be avoided.
When in contact with skin, these lasers don’t have any immediate effect but can cause heating effects at close range.
These lasers are most commonly used in laser light show projectors and some low-powered research lasers.
Class 4 Lasers
Class 4 lasers include all the lasers with a power rating of above 500 mW.
These are the most dangerous types of lasers that can cause permanent damage to the eyes and burn the skin.
Proper safety precautions must be taken while operating these lasers, as these lasers can be dangerous even when reflected off a matt surface.
Laser equipment with a Class 4 rating should be equipped with safety measures such as a key switch, an emergency stop button, and a safety interlock.
These lasers can also cause fire hazards if pointed towards a combustible material.
Most of the professional lasers used in the manufacturing and medical industry are class 4 lasers.
Laser Hazards you need to be aware of
While working with lasers, there are many things that can go wrong and lead to an accident.
It is necessary to be extremely careful while working with lasers as these accidents can cause severe damage to a human being.
Some of the most common laser hazards are:
- Eye exposure during the alignment of laser
- Misaligned laser beam
- Lack of personal protection equipment (PPE)
- Malfunctioning of the equipment
- Lack of an experienced operator
- Improper installation of the equipment
Eye and Skin Hazard
The eye is the most easily affected organ of the human body that a laser can damage.
Although in most cases, the blink reflex protects the eye from severe damage, some visible lasers can permanently damage the eye faster than the blink reflex.
Furthermore, the invisible laser beams, like in the case of infrared lasers, are not visible to the eyes and hence can cause severe damage as there is no bright light to instigate the blink reflex of the eye.
Depending upon the type of laser, its power, and duration of exposure, these lasers can also cause severe skin damage.
While some lasers may cause skin burns, other high-power lasers are capable of causing deep incisions along with the burning of the skin.
Fire Hazard
Laser beams directed towards a combustible material like paper, rubber, plastic, alcohol-based solution, etc., can sufficiently raise the temperature of the material to start a fire.
Fire hazards are common when the laser is used in an oxygen-rich atmosphere, like using oxygen as auxiliary gas while laser cutting thick material.
Electrical Hazards
Most high-power lasers are run by high voltage and high current electricity.
Improper handling of these equipment could lead to a risk of electric shock, and thus a highly trained individual is required to handle these equipment.
The ANSI Standard Z136.3 deals with the electrical safety procedures to be followed while operating laser equipment.
Gas Hazards
When treating a material under a laser, the gases or fumes produced by the burning and vaporizing material can be hazardous.
The intensity of damage caused by these gases depends on the type of material treated under the laser.
While the fumes produced by some materials only cause unpleasant odors, some can cause irritation to the lungs, and some can be poisonous if inhaled.
Safety Measures for Operating Lasers
Working with the equipment that uses class 3B or class 4 lasers can be extremely dangerous, and proper safety measures are necessary.
ANSI Standard Z136.1 deals with the safety program to be followed in the workplace while working with these lasers.
This safety program consists of three main components.
| Engineering | Administrative | Personal |
|---|---|---|
| Safety enclosure | Appointing Laser Safety Officer (LSO) | Safety glasses |
| Emergency stop button | Graphical warning signs | Gloves |
| Remote operation of the laser | Written laser safety policy | Protective clothing |
| Key switch | Standard operating procedures (SOP) | Safety respirators |
| Safety interlock | Periodic eye examination | Training for handling PPE |
Components of a laser safety program
Engineering Controls
These measures deal with the mechanical and design features of the laser equipment that restrict the chances of laser exposure.
It consists of features such as an emergency stop button, safety enclosure, remote operation of the laser, etc.
Administrative Measures
These measures deal with the informative and procedural aspects regarding the safe usage of laser equipment.
One of the most important administrative control is appointing a Laser Safety Officer (LSO) who ensures that proper safety measures are followed all the time.
Some other examples of administrative measures are using warning signs and labels wherever necessary, providing safety training to the staff, and establishing standard operations procedures (SOP).
Personal Protection
These measures deal with the safety gear that is to be worn by an individual while operating the laser or standing in the vicinity of lasers.
Some of the essential safety gear to be used are protective eyewear, gloves, protective clothing, and safety respirators (masks) to protect from harmful fumes.
The personal protection program also includes training the individual for the proper use and maintenance of personal protection equipment (PPE).
It should be noted that selecting the best laser safety glasses depends upon the wavelength of the laser used.
Frequently Asked Questions (FAQ)
Are class 1 lasers completely safe?
Yes, class 1 laser equipment are considered safe for use as they do not cause any harm to the eyes or the skin.
It should be noted that some class 1 laser equipment use a class 2M or class 3R laser inside a safety enclosure which makes it safe enough to be considered in class 1.
For example, the laser used in CD/DVD players can be a class 2M laser, but as the operation of the laser takes place inside an enclosure, a CD/DVD player is classified under class 1.
What is Maximum Permissible Exposure (MPE)?
Maximum permissible exposure (MPE) is the amount of laser energy or radiation that an individual can tolerate without any biological damage to the eyes or skin.
There are two different levels of MPE for a particular laser: one for the eyes and the other for the skin.
The various values of MPE for different wavelengths and durations of exposure to the laser beam are documented in the ANSI Z136 standards.
What are the duties of a Laser Safety Officer (LSO)?
The primary duty of a Laser Safety Officer (LSO) is to monitor the use of laser equipment and maintain safety by periodic inspection of the procedures. He is responsible for confirming the classification of the laser and setting up the appropriate procedures for using the laser.
He is also responsible for recommending the appropriate personal protection equipment (PPE) for that laser and posting appropriate warning labels wherever necessary.
It is mandatory to appoint a laser safety officer (LSO) if a class 3B or class 4 laser is used in the workplace.
