Exposure Limit (MPE) vs Emission Limit (AEL)
The eye exposure limit (MPE, ICNIRP 2013) against the Class 1 accessible emission limit (AEL, IEC 60825-1:2014) from 180 nm to 1 mm: where they agree, where they part, and how ANSI Z136.1 differs.
Educational only — not compliance-grade
These pages implement the published exposure limits for the cases each one states, but they are educational tools: no laser safety officer has signed them off.
- Do not use these results alone for PPE selection, NHZ / NOHD approval, controlled-area sign-off, enclosure/interlock approval, or formal classification.
- Always verify against ANSI Z136.1, IEC 60825-1, your local procedures, and the responsible laser safety officer / CLSO.
Exposure limit (MPE), ICNIRP 2013
10000 J/m²
Cornea (UV); for a beam inside the aperture, averaged over 3.50 mm, 100 W/m²
The same as energy through that aperture
96.2 mJ
962 µW for 100 s
Class 1 AEL, IEC 60825-1:2014
7.85 mJ
UV (IEC values, 1 mm stop); through 1.00 mm
AEL / exposure limit (as energy)
0.0816×
the product limit differs from the exposure limit here
Class 1 AEL for a CW laser
7.85 µW
over the time base, 30000 s; all of the beam inside the stop
The exposure limit and the Class 1 AEL for this duration, as energy through their apertures, 180 nm to 20 µm (log scales). They coincide except in the UV and from about 1300 to 1400 nm.
Two kinds of limit: the maximum permissible exposure (MPE) protects a person and is an irradiance or radiant exposure at the eye, averaged over an aperture (ICNIRP 2013, the MPE annex of IEC 60825-1, ANSI Z136.1). The accessible emission limit (AEL) classifies a product and is a power or energy through a measurement stop (IEC 60825-1). For Classes 1, 1M, 2, 2M and 3R the AEL is the MPE times the stop's area, so from 400 nm the two curves are mostly one. They part where IEC chose otherwise. In the UV it keeps its own values (a continuous C₂ = 10^(0.2(λ − 295)) J/m² at 302.5–315 nm, 10 W/m² after 10³ s at 315–400 nm) over a 1 mm stop at every duration, against ICNIRP's 1 nm steps and 1 → 3.5 mm aperture. ICNIRP also limits an eye-only exposure to the skin limit (twice it in the IR), which is lower than the retinal limit from about 1300 nm; IEC leaves that out of the classes and caps Classes 1 and 3R at the Class 3B AEL, 0.5 W through 7 mm, from 1250 nm.
A product also has a time base (100 s for Class 1 above 400 nm, 30 000 s in the UV): the CW AEL is the power that meets the AEL for every duration up to it.
ANSI Z136.1-2014 is harmonised with ICNIRP and IEC in most cases. Schulmeister (2017, p. 10) notes two differences: ANSI extrapolates its corneal limits from above 1400 nm to shorter wavelengths as a dual limit, and it raised the corneal limits up to 1500 nm for exposures under 10 s (by a factor of 3 below 1 ms). ANSI's tables are not public, so its values aren't computed here.
Model and references
Textbook approximation. A standard approximation from the literature (for example paraxial, plane-wave or Gaussian-beam), valid within the range the page states. About the tiers
MPE: least ICNIRP 2013 eye limit over its aperture. AEL: IEC 60825-1:2014 Class 1 rebuilt from it (IEC's own UV values, Class 3B cap at 1250–1400 nm). ANSI Z136.1 values not computed (tables not public).
- ICNIRP (2013). Guidelines on limits of exposure to laser radiation of wavelengths between 180 nm and 1,000 µm. Health Phys. 105(3), 271–295. Tables 2–5 and 8. doi:10.1097/HP.0b013e3182983fd4
- IEC 60825-1:2014. Safety of laser products – Part 1: Equipment classification and requirements. Tables 3–8 (AELs), Annex A (MPEs). webstore.iec.ch
- Schulmeister, K. (2017). The new edition of the international laser product safety standard IEC 60825-1. White paper, Seibersdorf Laboratories. AELs from the MPEs; ANSI Z136.1-2014 differences. seibersdorf-laboratories.at