Some of the lasers are potentially dangerous to humans and other living and non-living objects. Potential hazards to the eye and skin from laser radiation depend on the wavelength, exposure duration, and viewing conditions. Safety procedures are published in the American National Standards Institute ANZI Z136 series of standards and are followed by the U.S. Occupational Safety and Health Administration (OSHA). Information about safety standards and procedures can be obtained from: American National Standards Institute (ANSI), Laser Institute of America, IEC, and U.S. Department of Health & Human Services (FDA).

Powerful Handheld Laser - Wicked Lasers S3 KryptonLaser products are grouped into one of four general hazard classes listed below. Safety measures become more restrictive with increasing hazard class.

  • Class 1 Lasers – Very low power, eye-safe, output beam below maximum permissible exposure; safe to view.
  • Class 2 Lasers – Low-power visible lasers only; safe for brief (<0.25 s) viewing; intentional extended viewing is considered hazardous.
  • Class 3A Lasers – Medium power; safe for brief (<0.25 s) viewing; direct beam should not be viewed with magnifying optics such as a microscope, binoculars, or telescope.
  • Class 3B Lasers – Medium power; not safe for brief viewing of direct beam or specular reflections; control measures should eliminate this possibility.
  • Class 4 Lasers – High power; not safe for momentary viewing; potential for skin, fire, or diffuse reflection hazard.

Occupational exposure limits (ELs) are referred to as maximum permissible exposures (MPEs) by ANSI, as ELs by the World Health Organization and the International Radiation Protection Association, and as threshold limit values (TLVs) by the American Conference of Governmental Industrial Hygienists. All organizations recommend virtually identical exposure limits. Exposure limits are provided for exposure durations from one nanosecond to 8 hours and for wavelengths between 180 nm in the ultraviolet (at the extreme end of the vacuum ultraviolet band in the UV-C) to 1 mm in the extreme infrared IR-C band (at the edge of the microwave spectrum).

Summary of Biological Effects of Lasers

1. 190nm to 400nm Laser Beams

Laser Types: ArF, KrF, XeF (repetitively pulsed), He-Cd, Argon
Adverse Effects and Symptoms:
(A) Photokeratoconjunctivitis, normally reversible within 48 hr. Uncontrolled blinking, painful sensation of “sand” in eyes, inflammation of the cornea and conjunctiva, delayed in onset 6-12 hr. Reddening of skin (after delay).
(B) Erythema (sunburn), normally reversible within 1 week.
(C) Skin cancer. Delayed in onset by many years.
(D) Cataract of lens (300-315 nm). Delayed in onset by many years.
Maximal levels of exposure for a collimated laser beam: 3 mJ/cm2 for 200nm to 302nm for single or multiple pulse exposure; 0.56 t1/4 J/cm2 for 1 ns to 10 s;1 J/cm2 for single pulse or pulse train at 315nm. 0.56 t1/4 J/cm2 for 1 ns to 10 s; 1 J/cm2 for 10 sec to 1000 sec ; 1 mW/cm2 for 1000-s exposure or greater.

2. 400nm to 550nm Laser Beams

Laser Types: He-Cd, Argon
Adverse Effects and Symptoms: Retinal photochemical injury (“Blue-Light Injury”). Permanent scotoma in severe cases; some recovery after two to six weeks. Delayed onset of 24-48 hr. Retinal lesion visible by ophthalmoscope; blindspot (scoloma) also develops in 24-48 hr.
Maximal levels of exposure for a collimated laser beam: 10 mJ/cm2 for t = 10 s to 10,000 s; 1 mW/cm2 for t = 104 s (2.8 hr).

3. 400nm to 1400nm Laser Beams

Laser Types: Argon, Ruby, He-Ne, Nd:YAG, GaAs
Adverse Effects and Symptoms:
(A) Retinal thermal injury; permanent scotoma. Rapid appearance of ophthalmoscopically visible retinal lesion with associated blind spot that does not improve.
(B) Thermal burns of the skin. Rapid appearance of red spot (erythema) at site of exposure. Generally healing (sometimes with scar) within 4-6 weeks.
Maximal levels of exposure for a collimated laser beam: 5 mJ/cm2 at 1064 nm or 0.5 mJ/cm2 for t = 1 ns to 18 ms at 400 nm to 700 nm; 320 CA 1mW/cm2 for 700 – 1400 nm at t = 1000 s.

4. 1400nm to 1mm Laser Beams

Laser Types: HF, DF, Er, Ho, CO, CO2
Adverse Effects and Symptoms: Corneal thermal burns, skin burns. White flaky patch from pulsed laser near threshold; erythema from CW exposure to deep burn at much higher levels. Corneal vacuolization.
Maximal levels of exposure for a collimated laser beam: 10 mJ/cm2 for 1 ns to 100 ns.

Laser Protective Eyewear: Laser eye protection is necessary for all class 3B and 4 laser systems where exposure above the MPE is possible. ANSI Z136.1 provides general guidance for the use of eyewear.

Reference: “Hanbook of Lasers” by Marvin J. Weber