Understanding lasers

Lasers are beams of light, also known as optical radiation, that have unique qualities that make them useful in certain workplaces.

Monochromatic

Laser light is monochromatic. Monochromatic means that the beam is made up of one wavelength. If the wavelength is in the visible range of the spectrum (~380 to 740 nanometers (nm)), it is one colour. In contrast, white light, the type of light we use in our homes, is made up of all the various wavelengths of the visible spectrum.

Divergence

Laser beams do not diverge or expand quickly like other light does. Divergence is when the beam of light gets wider and less bright as you get farther away from the source. Like a flashlight or a regular light bulb in your home.

Laser beams do not diverge very much so the beam stays nearly the same size even a significant distance from the source. It also loses its brightness and energy more slowly than typical light sources.

Lasers in the workplace

Lasers are a very useful tool in industrial, medical and construction applications.

Workplaces use lasers for:

  • metal cutting and micromachining
  • therapeutic and aesthetic treatments such a hair removal, skin resurfacing, surgery
  • measuring and leveling devices used in construction, surveying

Key legal requirements

In Ontario, the Occupational Health and Safety Act covers the safe use of lasers in the workplace. There is no regulation specifically for lasers. Under the Occupational Health and Safety Act, employers must:

  • take every precaution reasonable in the circumstance to protect workers from hazards, including those related to the use of lasers
  • provide training on the safe use of lasers in your workplace to any worker who may be exposed to the hazards
  • when appointing a supervisor, appoint a competent person who is qualified because of knowledge, training and experience. He or she must also be familiar with the Occupational Health and Safety Act and any regulations under it that apply to the workplace, and know about any actual or potential health and safety hazards in the workplace.

Guidance documents for employers

Each of the following standards will provide guidance to employers on protecting workers from hazards related to lasers:

Hazards

The unique qualities of lasers that make them work well for different types of work can also cause injuries to workers. Workers may experience eye or skin injuries from contact with a direct or reflected laser beam.

If the beam of a Class 3B or Class 4 laser strikes unprotected skin, workers may experience an injury ranging from a mild burn to irreversible skin damage. The beam can heat or vaporize the tissue or cause cellular damage. Class 4 lasers can also cause permanent eye damage as a result of direct, diffuse, or indirect beam viewing.

The laser beam may be invisible, so you need to know the path of the laser beam when it is in operation.

Non-beam hazards

Lasers can create hazards in addition to the laser beam itself. If you have Class 3B or Class 4 lasers in the workplace you will need to evaluate the non-beam hazards as well as hazards from the laser beam itself. These non-beam hazards may include:

  • electrical hazards created by high-powered laser devices which may expose workers to electrical shock, sparks and hot surfaces
  • fire hazards present when using Class 4 lasers, and under special circumstances, Class 3B lasers. These lasers may ignite material that the beam strikes
  • laser plume such as vapours, smoke and particulate debris produced while workers use a laser for cutting, cauterizing, hair removal and many other procedures. The plume may contain carcinogenic airborne particles, toxic materials or biological agents like tissue or viruses
  • chemical hazards if you have lasers in your workplace that use dyes, coolants or solvents. It is important to have Safety Data Sheets (SDS) available for any chemicals used in the laser area if those chemicals are controlled under the Workplace Hazardous Materials Information System (WHMIS)
  • other radiation hazards such as ultraviolet, blue light, magnetic fields, microwave and even X-ray

Laser classification

There are different classes of lasers. The class of laser you have in your workplace will determine what reasonable precautions you should take to protect your workers.

Class 1/Class 1M

Class 1 lasers are considered safe under normal use. They are typically found in laser diodes in optical devices, such as DVD players and geological survey equipment. You may have a laser system that contains a high-powered laser, but the beam is entirely enclosed to prevent exposure to the direct or reflected beam. This kind of laser system is considered a Class 1 laser under normal use.

Workers can use a typical telescope or microscope to collect the beam of a Class 1 laser without risk of injury to their eyes or skin. You do not need to take any precautions to prevent harm to a worker with this type of laser other than to educate your workers regarding Class 1 lasers in the workplace.

Class 1M lasers are typically found in fibre optics. These lasers are also considered safe under normal viewing conditions, but this laser beam can cause injury to the eye if a worker views it through a telescope or microscope.

If you have Class 1M lasers in your workplace, some reasonable precautions that you may take, include:

  • worker education
  • appropriate signage such as “Laser radiation. Do not view directly with optical instrument"

Various guidance documents provide more detailed information regarding the reasonable precautions to protect workers from the hazards created by Class 1 and 1M lasers.

Class 2 and Class 2M

Laser levels and most barcode scanners in grocery stores are examples of Class 2 lasers. These lasers are in the “visible range”. Class 2 lasers emit light in the 400 – 700 nm range. This is the part of the optical radiation spectrum that we can see.

The visible spectrum is made up of the colours that we can see. It ranges from violet (400 – 420 nm) to red (620 -700 nm). Class 2 lasers only emit light in this range. If you look into or are accidently struck in the eye with a Class 2 laser, you will blink as a reaction to the bright light. This is called the “blink reflex” and it takes less than ¼ of a second. Your blink reflex protects your eye against injury because of the limited time of exposure to the beam (less than ¼ second).

The maximum power for a Class 2 laser is 1 milliWatt (mW) for a continuous wave. You should never deliberately stare into the beam. This can cause injury to the retina in the back of the eye. Additionally, if you have any workers who have a delayed blink reflex (this may be associated with some neurological conditions or paralysis), they may be at risk of an injury from a Class 2 laser.

Class 2M lasers are lasers that are within the visible range (400-700 nm) and are considered safe under normal conditions because of the blink reflex. However, these lasers present a hazard if a worker views the beam through an optical device like a telescope or a microscope.

If you have Class 2 or Class 2M lasers in your workplace, some reasonable precautions that you may take, include:

  • worker education
  • signage such as, “Laser radiation. Do not stare into beam. Class 2 laser product” or “Laser radiation. Do not stare into beam or view directly with optical instruments. Class 2M laser product”

Various guidance documents provide more detailed information regarding reasonable precautions you may take to protect workers from the hazards created by Class 2 and 2M lasers.

Class 3R

Laser pointers are often Class 3R lasers. Your blink reflex will protect you from this type of laser, but you may experience temporary “flash blindness”.

Class 3R lasers may have a visible or invisible laser beam. The visible beam (between 400 – 700 nm) lasers have no more than 5 mW of continuous wave power. These lasers are generally not considered to be a significant hazard if workers do not view them with optical devices like telescopes or microscopes. Class 3R lasers generally do not cause permanent damage.

If you have Class 3R lasers in your workplace, some reasonable precautions that you may take, include:

  • worker education
  • signage, such as “Laser radiation - avoid direct eye exposure. Class 3R laser product”

Class 3B

Class 3B lasers are often used in spectrometry and in some laser hair removal systems. These lasers can cause injury to skin or eyes from direct or indirect (reflected) exposure to the beam. When appointing a supervisor, you must appoint a competent person, such as a supervisor, who ensures workers are aware of and protected from the hazards of Class 3B lasers.

Class 3B lasers beams can be visible or invisible and have a continuous wave power of greater than 5 mW but not more than 500 mW (0.5 W). These lasers have the potential to cause immediate injury to eye and skin if a worker’s eye is exposed to the direct laser beam or to a reflection of the beam from a mirror-like surface. If the beam is reflected from a matte surface like paper or matte paint (often referred to as a “diffuse reflection”), it is unlikely to cause any injury.

The exposure limits from a Class 3B laser vary depending on the wavelength of the light and whether the laser is a continuous beam or a pulsed laser.

If you have a Class 3B laser in your workplace, we encourage you to familiarize yourself with laser guidance documents such as those from ANSI or CSA.  These types of documents provide guidance on how to set up a laser safety program. A typical laser safety program would include:

  • identification of a supervisor
  • education and training on the safe use of lasers
  • protective measures to control laser hazards
  • incident investigation
  • a medical surveillance program, if applicable
  • a laser safety committee if the hazard or diversity of the lasers is complex

Class 4

Class 4 lasers are used for:

  • surgery
  • cosmetic skin treatments and tattoo removal
  • university research
  • drilling
  • cutting
  • welding
  • micromachining

These lasers are the most powerful and hazardous of all the laser classes. Exposure to the beam or a reflection of the beam will cause immediate injury to the eye and skin. When appointing a supervisor, you must appoint a competent person to ensure that:

  • workers are aware of the hazards
  • workers use or wear protective devices, such as appropriate laser goggles, that the worker’s employer requires to be worn
  • every precaution reasonable in the circumstances is in place to protect workers from injury

Class 4 lasers cause immediate injury to eye and skin if a worker is exposed to the beam or the reflection of the beam from either a shiny or dull surface. They also pose “non-beam” hazards, such as the possibility of:

  • fire
  • exposure to high voltage
  • exposure to the “laser plume” (the vapours, smoke and particulate debris created by the laser)

You must take all precautions reasonable in the circumstances to protect your workers from both the beam and non-beam hazards of Class 4 lasers. A laser safety program should contain all necessary information regarding the hazards and the controls that you have in place to protect workers.

Appointing a competent person as supervisor

If you have Class 3B or 4 lasers in the workplace, and you appoint a supervisor, you must appoint a competent person. The supervisor would have authority over lasers in the workplace. This person has the training, knowledge and understanding of lasers and laser safety to oversee the laser safety program.

The supervisor is responsible for:

  • assessing the hazards created by lasers
  • ensuring that appropriate calculations are completed for each Class 3B or 4 lasers in the workplace, such as:
  • assisting in determining the appropriate safety eyewear

One way the laser supervisor can demonstrate competency is to complete a laser safety training program. The level and depth of the laser safety training should be linked to the level of hazard associated with the laser.  A typical laser safety program should include:

  • relevant legislation and standards that are available such as those from CSA and ANSI
  • laser hazards including beam, reflection and non-beam hazards
  • effect on tissue and the eyes when exposed
  • risk assessment of laser hazards including maximum permissible exposure (MPE)
  • control measure of laser hazards
  • the elements of a laser safety program

 The vendor of the laser system may be able to refer you to appropriate training.

Hierarchy of controls

You must take every precaution reasonable in the circumstances to protect your workers from the hazards created by Class 3B and 4 lasers. You use the “hierarchy of controls” to protect workers from hazards.

The hierarchy of controls is a system used to minimize or eliminate hazards. You start with the highest level of control possible to protect workers. The order of controls is:

  • elimination
  • substitution
  • engineering controls
  • administrative and procedural controls
  • personal protective equipment (PPE)

If you have a laser in your workplace, it is unlikely that elimination or substitution are options. Consider when you will use engineering, administrative and procedural controls and personal protective equipment.

Engineering controls

Engineering controls are controls that are built into the laser systems or controlled areas, for example:

  • interlocks that prevent the laser from operating if the beam is not enclosed or if the protective cover is removed
  • an interlock on a doorway into the laser area that shuts down the laser or blocks the beam entirely if the door is opened during operation

You should consider engineering controls as the first line of defense. Move to the next option on the list if it is not possible to eliminate the hazard with engineering controls.

Administrative and procedural controls

These controls are intended to reduce the severity or effect of the hazard. Examples include:

  • work procedures
  • competent supervision
  • signage, such as danger or warning signs on every entry into a Class 3B or 4 laser room
  • training
  • lights that illuminate when the laser is in operation
  • a list of approved users

Personal protective equipment

Personal protective equipment is considered the last line of defense against hazards. You use personal protective equipment, such as laser safety goggles, after you have controlled the hazards as much as possible with engineering, administrative and procedural controls.

Beams from Class 3B and 4 lasers will cause injury to eyes and skin. Workers who are in the hazard zone of a Class 3B or Class 4 laser must wear appropriate laser safety goggles.

Laser eye incidents may occur if:

  • workers are not wearing protective eyewear
  • the eyewear is damaged
  • workers are using incorrect eyewear for the laser

You can determine the appropriate safety glasses depending on the wavelength and power of the laser in use. The manual that came with the laser will also have information regarding appropriate safety eyewear.

Definitions

Continuous wave laser: a laser that emits a continuous, uninterrupted beam of light with a stable output power.

Maximum permissible exposure(MPE): the level of laser radiation to which an unprotected person may be exposed without adverse biological changes in the eye or skin.

Nominal hazard zone (NHZ): the space within which the level of the direct, reflected, or scattered radiation may exceed the applicable MPE. Exposure levels beyond the boundary of the NHZ are below the appropriate MPE.

Pulsed laser: a laser which delivers its energy in the form of a single pulse or a train of pulses. In this standard, the duration of a pulse is less than 0.25 s.