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North Safety Glossary for Eye and Face Protection

North Safety Glossary for Eye and Face Protection


North Safety product managers have compiled the following helpful terms as a reference for our customers.  Some of the terms have been adapted from OSHA's guidelines.

Base Curve - The degree of curve in a safety glass lens. The base curve number is the degree of arc.

Blue Light - Visible light or radiation in the median portion of the spectrum that may cause retinal damage.

Chin Protector - The portion of a device that offers protection to the wearer's chin, lower face and neck.  

Crown Protector -  The portion of a device that offers protection to the wearer's forehead.

Crown Strap -  The portion of headgear that rests on top of the head.

Dark State - The lowest operating luminous transmittance of an automatic darkening filter lens.

Diopter (D) - The unit of measurement (plus or minus) used to express the power of a lens. The diopter is also used to express the curvature of surfacing tools and the refracting power of curved surfaces in eyewear..

Eye Protection - Safety glasses, chemical splash goggles, or face shields which are used when handling  hazardous materials or in an area of falling debris or where there is a chance of eye injury.

Faceshield - A protective device commonly intended to shield the wearer's face, or portions thereof, in addition to the eyes, from certain hazards, depending on faceshield type. Faceshields can only be used in conjunction with spectacles and/or goggles.

Filters - Lenses that reduce or eliminate light intensity.      

Flexi-Fit Nosepiece - North's flexible, silicone nose bridge which fits a wide variety of wearers and resists slipping. Used on the safety eyewear styles which accept the RX insert nosepiece.

Frame - A device which holds the lens or lenses on the wearer.

Glare - Uncomfortably bright light.

Goggle - A protective form of eyewear designed to protect the eyes and seal to the surrounding face. They provide protection in situations where safety glasses alone may not, for example, in chemical splash hazard areas.   

Haze - The percent of incident light that is not transmitted in a straight line through the lens.

Headgear - The part of a protective helmet, hood or faceshield that supports the device on the wearer's head.

High Impact Protectors/Lenses - Protectors that are used in an environment where the known or presumed hazards are from high velocity, or high mass impact.

IR (Infrared Radiation) - A type of radiant energy or electromagnetic radiation with a wavelength from 780nm to 2000nm.

Interpupillary Distance (PD) - The distance in millimeters between the centers of the pupils of the eyes.

LASER - An acronym for Light Amplification by Stimulated Emission of Radiation.

Lens - The transparent portion of safety glasses, face shields or goggles through which the wearer can see..

Light Absorption - The process by which light is reduced by passing through a lens.

Light Transmission - The amount of light reaching the eye after passing through a filter.

Nanometer (nm) - A unit of measurement of wavelength equal to one billionth of a meter.

Optical Radiation - The portion of the electromagnetic standard ranging in wavelength from 200nm to 2000nm, having the nominal sub-intervals of UV-C (200-280nm), UV-B (280-315nm), UV-A (315-380nm), VISIBLE (380-780nm), IR-A (780-1400nm), IR-B (1400-3000nm), and IR-C (3000nm-1mm).

PETG - Faceshield material, for use in heat generating applications, when not exceeding 140 degrees F. Also provides good chemical resistance.

Plano Lens - A lens that does not incorporate a prescription for vision correction.

Polycarbonate - Extremely impact resistant material, with excellent weathering and heat resistance up to 250 degrees F and high clarity.

Refractive Power - A measure of the ability of the lens to focus light rays, expressed in diopters (D).

Resolving Power (definition) - The measure of the ability of a lens to form separate distinct images of two objects close together.

RX Insert - North's prescription eyewear insert designed to fit into any of 3 styles of North eyewear.   

Side Shields
- Shields added to eye protection to provide side protection.

Temples - The part of a spectacle frame commonly attached to the front and generally extending behind the wearer's ear.

UV (Ultraviolet) - Those wavelengths of the electromagnetic spectrum that are shorter than those of visible light and longer than X-rays. The wavelengths of UV radiation are 200nm to 380nm.

Unilens - A design for safety eyewear with a single piece lens to cover both eyes; generally provides wide view.

Universal Fit Nosepiece - North's polycarbonate nose bridge which fits most wearers.

Vinyl - A class of resins that are soft and flexible.  It  is often used to make goggles.

Visible Light - A form of radiant energy that is visible to the human eye; has a wavelength of 380nm to 760nm.

Visual Acuity - The ability of the eye to sharply perceive the shape of objects in the direct line of vision.

Welding Helmet - A protective device intended to provide protection for the eyes and face against optical radiation and weld spatter. Should be worn only in conjunction with spectacles or goggles.

Window - The lens portion of a faceshield.