Science, Technology and Engineering - Nightlase Technologies

Laser Safety

One of the most important factors when working with lasers are the safety considerations and minimisation of risks of injury.

Lasers pose the most risk to our eyesight, even small powered (low energy density) lasers in the milliwatt output range can produce enough laser light to cause permanent damage to the retina.

Lasers produce optical energies from ultra-violet, visible and infrared parts of the electromagnetic spectrum, and either as a pulsed or continuous wave (CW) output.

The effects lasers have on biological tissue, through various mechanisms, is influenced by their wavelengths and their output (optical power, CW vs Pulsed).

High-power lasers also present a risk to the skin via photochemical or thermal burns. Depending on the wavelength, the beam may penetrate both the epidermis and the dermis. Ultra-violet lasers present a risk to the epidermis with similar effects as a "sunburn".

The topic on Laser safety is a considerable subject area, and furthermore, the important criteria of calculating the Maximum Permissible Exposure (MPE); the highest power or energy density (in W/cm² or J/cm²) of a light source that is considered safe, can be rather complex.

The following list summarises the pathological effect to the eye caused by lasers operating at different wavelengths.

Ultra-violet lasers (180nm-400nm) pose risks to the cornea and lens (photokeratitis and cataract).
Visible lasers (400nm-780nm) pose risks to the retina and cause retinal burns.
Infrared lasers (780nm-1mm) capable of affecting most of the eye.

Classification of Laser Hazards

The main risk of lasers is that they pose a hazard to the eyes. Due to the nature of lasers beams being very directional sources of light, capable of high energy levels in a very small area. When lasers are focused, this energy is focused into a much smaller area.

The pupil of the eye varies from 2mm in bright conditions to 8mm for a dark-adapted eye. Many lasers will generate beams that fall within these values, therefore the total energy from a laser is focused onto the retina.

Lasers producing optical output in the infrared part of the spectrum are the most hazardous as their beams are invisible, with Q-switched and pulsed lasers having greater risk again as they generate high-peak power levels.

Lasers are classified by the amount of radiation that is emitted, wavelength and pulse characteristics.

Class	Potential Hazards
Class 1	Inherently safe under normal conditions, may cause dazzling visual effect.
Class 1M	As per Class 1, Eye injury may occur when beams viewed with optical magnifiers.
Class 1C (Australia, QLD)	Cosmetic or medical lasers intended for direct application of radiation to the skin or internal body tissues. - Eye injury prevented by engineering means. - Exposure of the skin depends on how the laser is used.
Class 2	Low Hazard; Eye damage is prevented by blink reflex (0.25 sec exposure).
Class 2M	As per Class 2, Eye injury may occur when beams viewed with optical magnifiers.
Class 3R (upto 5mW)	Visible radiation, Eye damage may result from viewing direct and reflected beams. Blink reflex protection.
Class 3B (upto 500mW)	Eye damage may result from viewing direct and reflected beams. Minor hazard to skin is possible.
Class 4 (> 500mW)	Skin and eye hardards from exposure to direct and indirect (reflected) beams. Eye hazards from diffused reflections. Additional risks include potential fire hazards to combustable materials. High-powered lasers can generate hazardous laser plumes.

Note: The above table is the revised laser classification from 2003. Prior, the old classification was used.

Labling for Laser Equipment

All Laser equipment require radiation labels to advise and warn users, operators and service personnel of a laser device to the potential hazards involved with the radiation source.

In Australia, the requirements for labelling of laser products are described in the Australian / New Zealand standards for safety of laser products

AS/NZS IEC 60825.1:2014 Safety of Laser Products - Equipment classification and requirements
AS/NZS IEC 60825.14:2011 Safety of Laser Products - A User's Guide
AS/NZS IEC 2211.10:2004.14:2011 Safety in Laser Products. Part 10: Application guidelines and explanatory notes to AS/NZS 2211.1(IEC TR 60825-10:2002, MOD)

In Australia, the US signage (blue/white and red/white) is not acceptable for use.

All laser equipment requires three types of radiation hazard labels:

Laser Warning Label (Laser star/burst symbol inside triangle).
Explanatory label (a written description of the hazard, which may include directions to avoid exposure).
Aperture label (to identify where the radiation is being emitted).

Class 1 Laser Labels