What does NOHD (Nominal Ocular Hazard Distance) mean?

NOHD is the distance from the laser at which the beam irradiance equals the Maximum Permissible Exposure (MPE) for the eye. Within this distance, eye protection is mandatory. For a 6kW fiber laser, NOHD can exceed 100 meters for the direct beam. However, inside a properly enclosed laser machine, the NOHD is effectively zero since the beam is fully contained. Understanding NOHD is critical for service/maintenance when enclosures are open.

What optical density (OD) eyewear do I need for laser safety?

OD requirement depends on laser power, wavelength, and exposure duration. For industrial cutting lasers: Class 4 at 1070nm (fiber): OD 6+ required. Class 4 at 10600nm (CO₂): OD 5+ required. The formula is OD = log₁₀(H₀/MPE) where H₀ is the irradiance. Always select eyewear rated for your specific wavelength range - using wrong wavelength eyewear provides NO protection.

Is my laser machine enclosure sufficient for Class 4 safety?

Per IEC 60825-1 and OSHA requirements, Class 4 laser enclosures must: 1) Fully contain the beam during normal operation. 2) Have interlocked access panels that disable laser when opened. 3) Include warning indicators when laser is energized. 4) Prevent specular reflections from escaping. 5) Use appropriate materials (not reflective or combustible). Most OEM cutting machines are designed to reduce external classification to Class 1 (embedded system), but maintenance access requires full Class 4 precautions.

Laser Safety Class Calculator (IEC 60825-1)

⚠️ Quick Answer: Industrial Laser Safety

All industrial cutting/welding lasers (>500mW) are Class 4 - the highest hazard level. Requires full enclosure, interlocks, OD 5-7 eyewear, and Laser Safety Officer (LSO) designation.

Determine your laser safety classification per IEC 60825-1:2014 and ANSI Z136.1-2022 standards. Get required protective measures and labeling requirements.

Laser Power (W)

Wavelength (nm)

Beam Diameter (mm)

Exposure (s)

Laser Type

Common wavelengths: Fiber 1070nm | Nd:YAG 1064nm | CO₂ 10600nm | Green 532nm

Safety Classification

Enter laser parameters to determine safety classification.

IEC 60825-1 Laser Safety Classes

Class	Power/Energy Limit	Hazard Level	Required Controls
Class 1	< 0.39 mW (visible)	Minimal	No special controls - inherently safe
Class 2	< 1 mW (visible only)	Low	Warning labels, avoid staring into beam
Class 3R	< 5 mW (visible)	Moderate	Warning signs, limit direct exposure, training
Class 3B	< 500 mW	High	Laser eyewear (OD 4+), controlled area, key switch
Class 4	> 500 mW (all industrial)	Extreme	Full enclosure, interlocks, LSO, OD 5-7 eyewear, fire suppression

Class 4 Laser Safety Requirements

Engineering Controls

• Full beam enclosure during operation
• Interlocked access panels (laser disables when open)
• Key switch or code-controlled activation
• Warning light indicators (laser energized)
• Emergency stop accessible from all sides
• Beam stops and beam dumps

Administrative Controls

• Designated Laser Safety Officer (LSO)
• Written Standard Operating Procedures (SOP)
• Laser safety training for all operators
• Controlled access area with warning signs
• Proper labeling per IEC 60825-1
• Maintenance log and incident reporting

Laser Safety Eyewear OD Requirements

Laser Type	Wavelength	Minimum OD	VLT Consideration
Fiber Laser	1064-1080 nm	OD 5+ (typical OD 6-7)	High VLT possible (70%+)
Nd:YAG	1064 nm	OD 5+ (typical OD 6)	High VLT possible
CO₂ Laser	10600 nm	OD 5+ (typical OD 5-6)	Clear lenses available
Green Laser	532 nm	OD 4-5	Lower VLT (orange/red tint)

OD = Optical Density. OD 5 = blocks 99.999% of radiation. Always verify eyewear rating matches your exact wavelength.

Frequently Asked Questions

A 6kW fiber laser (1070nm) is definitively Class 4 - the highest hazard class. Class 4 lasers can cause immediate eye injury from direct or reflected beams, skin burns, and fire hazards. Required safety measures include: full enclosure with interlocks, laser safety eyewear (OD 6+ at 1070nm), LSO designation, key switch control, warning signs, and written safety procedures. All industrial cutting and welding lasers above 500mW are Class 4.

Related Tools & Guides

Power Density Calculator

Calculate beam intensity for hazard assessment

Beam Quality Analyzer

M² analysis affects beam divergence and safety zones

Laser Type Wizard

Compare fiber, CO₂, and solid-state safety considerations

Laser Safety Classes Guide

Comprehensive guide to IEC 60825-1 classification

Safety Operations Guide

Best practices for Class 4 laser operation

Installation Requirements

Facility requirements for industrial lasers

⚠️ Important: This tool provides estimates based on IEC 60825-1:2014 simplified thresholds. Actual safety classification requires detailed analysis including pulse parameters, beam divergence, and viewing conditions. Always consult a qualified Laser Safety Officer (LSO) and refer to official standards (IEC 60825-1, ANSI Z136.1) for compliance.