TRANSMISSION FACTOR (VLT)

The colour of the lenses plays a fundamental role in the management of brightness in the different work activities and in any environments in which they are used. With reference to this, EN ISO 12312-1:2022 European Standard (Eye and face protection-Sunglasses and related devices Part 1: Sunglasses for general use) classifies glasses in 5 categories from 0 to 4 based on VLT (Visible Light Transmission). This value indicates the light quantity transmitted to the eyes through the lenses, it is affected by the colour, by the thickness, by material and by treatments of lenses.

CATEGORY	COLOUR	VLT(%)	DESCRIPTION AND INSTRUCTIONS FOR USE
0	Clear or lightly coloured/darkened lenses	80÷100		Very limited reduction of sunlight
1	Lightly coloured/darkened lenses	43÷80		Limited reduction of sunlight
2	Medium coloured/darkened lenses	18÷43		Good protection against sunlight
3	Dark lenses	8÷18		High protection against sunlight
4	Very dark lenses	3÷8		Very high protection against sunlight (sea, snow, mountain or desert). Not recommended for driving and for street use

LENSES COLOUR

The effects of an unsuitable protective filter colour may cause: decrease of visual acuity, sensation of effort, headache and even nausea and dizziness. Different colours of the lenses allow to promote or preserve the perception of colours, of contrasts and visual acuity; furthermore, they may reduce reverberation and remove UV rays.

COLOUR	SCALE NUMBER	VLT(%)	DIRECTIONS
CLEAR	2C-1,2	88÷92	Recommended for indoor environments with good visibility conditions and for indoor applications, where the protection of the eyes against impact and most common risks is recommended. Moreover, they help to protect against ultraviolet rays. Applications: mechanical indoor work with good visibility conditions.
YELLOW	2C-1,2 2-1,2	86÷88	Recommended for low-light conditions, cloudiness, mist or fog, seeing as in such conditions, it allows to make objects more visible. Beside perfectly filtering ultraviolet rays (UV) and the blue portion (up to 480 nm) of the visible spectrum, it increases contrast even in low-light conditions. Applications: works in bad weather conditions and in foggy environments, inspection of surfaces, working in tunnels, subsoil working, mines, mechanical working, ultraviolet light exposure, warehouses.
I/O (INDOOR/ OUTDOOR)	2C-1,4  5-1,7	57÷68	Recommended for anyone frequently passing from indoor (closed and with low light) to outdoor environments (open-air and quite enlightened) and vice versa. Being a clear lens with a light mirrored treatment, it provides optimal view in both indoor and outdoor lighting conditions. This lens allows, therefore, a greater visibility and a high identification of colours and shapes during the use in both conditions and during the passage through these two environments. Applications: works with forklift truck, mechanical works, works with the passage between dark and bright environments.
GREY	5-2,5 5-3,1	9÷26	Recommended for well-lighted environments where light causes a considerable eye strain. It greatly absorbs both ultraviolet rays (UV) and infrared ones (IR), beside keeping the relative proportions among colours. The absorption is almost constant in the visible spectrum while the wavelength changes, so that the chromatic perception is only slightly altered. Applications: outdoor works, mechanical works with risk of glare, agriculture, building, refineries.
BROWN	5-3,1	9	Recommended for works in sufficiently lit environments where light can cause eye strain. It protects sufficiently both against ultraviolet (UV) and infrared (IR) rays. Moreover, by filtering discreetly the most energic area of the visible spectrum (blue), it favours the contrast in foggy conditions. It allows a good colour identification with optimum contrast. Applications: outdoor works, mechanical works with risk of glare, agriculture, building, refineries.
MIRRORED (BLUE, RED, SILVER, GOLD)	5-2,5 5-3,1	12÷24	Recommended for environments where it is necessary to be protected against intense sunlight, glare, reverberation and all those elements which cause considerable eye strain. The mirrored treatment on the outer surface of the lens reduces transmittance through a greater reflection of the light hitting the lenses. It is obtained, therefore, a significant reduction of the quantity of light that reaches the eyes, getting a high benefit and a visual comfort even after an extended use. Applications: outdoor works with intense sunlight and with risk of glare, agriculture, building, refineries.
REVO (BLUE, GREEN, SILVER)	5-3,1	9÷14	Recommended for outdoor works with very intense and annoying light condition which disturbs the sight causing eye strain. REVO treatment, done on the external surface of the lens, improves visual performance, protects against ultraviolet (UVA and UVB) and infrared (IR) radiations, grants an excellent abrasion resistance and long-lasting adhesion. Applications: outdoor works with very intense light and with risk of glare, building and construction, waste collection, agriculture, fishing.
POLARIZED (GREY, BROWN)	5-3,1	9÷15	Recommended for intense light and high glow caused by reflective surfaces. Such situations cause a remarkable decrease in eyesight and consequently a considerable eye strain. This type of lens is able to let the light pass selectively; indeed, acting like “Venetian blinds”, they reduce the overall quantity of light passing through and let only the “useful” light pass through. In this way, reverberation is notably reduced and it is increased the quality of images which appear brighter, consequently even the visual perception is improved. Applications: outdoor works with a high risk of glare, construction site, road work, driving vehicles, oil-plants, work on highly reflective surfaces (water, ice, snow, sand and street surface).
WELD 3 WELD 5	3 5	2÷9	Recommended for protection against impacts, ultraviolet rays (UV), infrared rays (IR) and dazzling caused by welding processes. Applications: works in welding and brazing departments (WELD 3: brazing and gas welding; WELD 5: gas and oxyfuel welding, foundries and furnaces).

LENS CURVATURE

A further plus of lenses improving comfort is the curvature (up to base 10). The curvature index defines the difference between more or less wrap-around lenses. Indeed, it results that more wrap-around lenses and so with a greater curvature have a wider and clearer field of view due to a reduction of distortions and aberrations of typical images of less wrap-around lenses and with not high curvature. It results an improvement of visual quality as well as the clarity of peripheral vision of the user.

LENSES TREATMENTS

	ANTI-SCRATCH TREATMENT Hardening treatment carried out on the surfaces of the lenses which determines an improvement in terms of resistance against abrasion and therefore, a longer duration in time.
	ANTI-SCRATCH TREATMENT PLUS Hardening treatment carried out on the surfaces of the lenses which determines an improvement in terms of resistance against abrasion and therefore, a longer duration in time. In conformity with the optional EN 166 requirements, eyepieces with anti-scratch treatment PLUS satisfy resistance parameters to the damage of surface caused by thin particles (whose minimum provided requirement is a luminance factor lower than 5 cd/(m2·lx)), thus offering definitely higher performance compared to the standard anti-scratch treatments on the marketplace. COFRA indicates such performances by specifying the maximum luminance factor (expressed in cd/(m2·lx)) tested by the certification bodies. Therefore, such eyepieces may be marked with the symbol “K”.
	ANTI-FOG TREATMENT Treatment carried out on the surface of lenses which prevents fogging and, being able to spread condensation formed on the surfaces of the lenses in the passage from cold to hot environments, improves the visibility in critical conditions.
	ANTI-FOG TREATMENT PLUS Treatment carried out on the surface of lenses which prevents fogging and, being able to spread condensation formed on the surfaces of the lenses in the passage from cold to hot environments, improves the visibility in critical conditions. In conformity with the optional EN 166 requirements, eyepieces with anti-fog treatment PLUS satisfy resistance parameters against fogging (whose minimum provided requirement is a resistance for at least 8 s), thus offering definitely higher performance compared to the standard anti-fog treatment on the marketplace. COFRA indicates such performances by specifying the minimum time of resistance to fogging (expressed in seconds) tested by the certification bodies. Therefore such eyepieces may be marked with the symbol “N”.
	UV400 PROTECTION UV400 protection extends protection of lenses beyond the conventional block, rated 380 nm. Such treatment, indeed, allows to filter UV radiations beyond this wavelength, blocking the transmittance of the light spectrum up to 400 nm and helping to protect eyes from a wider range of harmful light rays.
	MIRRORED TREATMENT Carried out externally to the lens, covered with a thin partially reflecting layer, it is a treatment that allows a greater reflection of incident light on the lens itself, reducing most of the light that reaches the eyes. This treatment is suitable and recommended for use in conditions of extremely strong light and where it is necessary to be protected against glare (snow and ice).
	REVO TREATMENT Multi-layer coating made on the external surface of lens. It allows to reflect to a high degree that particularly intense and annoying light that disturbs the sight provoking a considerable eye strain. REVO treatment improves visual performance, protects against ultraviolet (UVA and UVB) and infrared (IR) radiations dangerous for eyes, and grants an excellent abrasion resistance and a long-lasting adhesion. This treatment is suitable and recommended for all outdoor activities requiring high visual comfort and protection against sources of intense light.
	HYDROPHOBIC TREATMENT Excellent water-repellent treatment performed on the surface of the lenses through a vacuum process that creates a thin and transparent film. The unique formula used during this process provides exceptional water repellency, making the lenses suitable for all those activities where there is high humidity, such as fishing. It can be applied to simple lenses or on the outer layer of any mirrored or REVO lens.
	HYDROPHOBIC + OLEOPHOBIC TREATMENT Innovative treatment able to combine both water and oil repellence. This treatment acts as an invisible protective film that can protects the surface of the lens. It can be applied to simple lenses or on the outer layer of any mirrored or REVO lens. This treatment provides the lenses with many advantages: water and oil repellence; resistance to stains and fingerprints; easy cleaning; abrasion resistance caused by particles or dust.
	POLARIZING FILTER The polarizing filter is a filter of polarized lenses that reduces eye strain caused by sources of glare and/or glass or reflective surfaces (water, ice, snow, sand, road surface). The result is an increased visual comfort, a higher optical quality and a better contrast of colors, making them more vivid and clear.

FRAME FEATURES

	EXTENDIBLE TEMPLES It consists of a system for length regulation of the temples that allows glasses to adapt optimally to the face of the wearer, thus ensuring the best comfort.
	ADJUSTABLE TEMPLES It consists of a system for grade regulation of the temples that allows glasses to adapt optimally to the face of the wearer, thus ensuring the best comfort.
	INTERCHANGEABLE SYSTEM OF TEMPLES/ELASTIC BAND The eye protectors with this system give the possibility to replace the temples with the elastic band and vice versa. In this way, these eye protectors can carry out the function of safety glasses if they are worn with the temples, but at the same time they could be similar to goggles/masks when worn with an elastic band.
	ADJUSTABLE NOSE PAD Soft nose pad equipped with a metal core that allows to adjust and adapt it to any face structure. The result is a comfortable fit for a wide range of nose bridges, avoiding eye strain.
	SOFT NOSE PAD The soft rubber used for the nose pad improves the comfort of glasses, allowing a prolonged use.
	EYEBROW PROTECTION Protection system which, thanks to its softness, makes glasses more comfortable and provides an excellent impactprotection against high-speed particles or against accidental and frontal impacts of the operator.
	SOFT EAR PIECES Situated at the end of temples and made up of soft rubber, they reduce the pressure of the temples on the head of the operator, ensuring a better adherence and a greater comfort especially in case of prolonged use.
	VENTILATION SYSTEM System which, permitting the air to flow, allows to minimize the fogging effect.

Scale number

The filter code number is always followed by the filter rating number (both numbers are separated by a space), and together form the scale number.

APPLICATION FIELDS

SYMBOL	PROTECTION AGAINST	DESCRIPTION OF THE APPLICATION FIELD	TYPE OF EYE PROTECTOR
			Glasses	Goggles/Masks	Face masks
none	Basic	Unspecified mechanical hazards and dangers deriving from ultraviolet, visible, infrared and solar radiations
3*	Liquids	Droplets of liquid	Not applicable		Not applicable
		Splashes of liquid	Not applicable	Not applicable
4*	Dust particles of big dimensions	Powder with particles > 5 μm	Not applicable		Not applicable
5*	Gas and particles of fine dust	Gases, vapors, sprays, fume and dust with particles < 5 μm	Not applicable		Not applicable
8**	Short circuit electric arc	Electric arc due to short-circuit in the electrical system	Not applicable	Not applicable
9***	Molten metals and hot solids	Liquid metal splashes and penetration of hot solids	Not applicable

* The symbol (s) 3, 4 and 5 must be indicated on the frame. If the frame of the eye protector is not marked with any of these symbols, then the eye protector is not intended to be suitable for protection against chemical risks.

** The symbol 8 must be indicated on the lens and on the frame to guarantee protection against electrical risks. To conform to symbol 8, a face shield must be equipped with a filter with a scale number of 2-1,2 or 3-1,2 and have a minimum thickness of 1,4 mm.

*** The symbol 9 must be indicated on the lens and on the frame to guarantee protection against thermal risks. To conform to symbol 9, both the frame and the eyepiece must be marked with this symbol together with one of the following symbols: F, B or A.

OPTICAL CLASS (All COFRA lenses are optical class 1)

MECHANICAL RESISTANCE

SYMBOL	IMPACT		TYPE OF EYE PROTECTOR
	Impact level	Impact speed	Glasses	Goggles/Masks	Face masks
A* AT**	High energy impact	190 m/s (684 km/h) Steel ball with a diameter of 6 mm and a mass of 0,86 g	Not applicable	Not applicable
B* BT**	Medium energy impact	120 m/s (432 km/h) Steel ball with a diameter of 6 mm and a mass of 0,86 g	Not applicable
F* FT**	Low energy impact	45 m/s (162 km/h) Steel ball with a diameter of  6 mm and a mass of 0,86 g
S	Increased resistance specification	5,1 m/s (18,36 km/h) Steel ball with a diameter of  22 mm and a mass of 43 g
none	Minimum resistance specification

* If the symbol F, B or A is not found on both the lenses and the frame, then the lower value is assigned to the complete set of safety glasses.

** If protection is required against high speed particles at extreme temperatures (-5 °C and +55 °C), then the safety glasses should be marked with the letter T immediately following the letter indicating the impact resistance, i.e. FT, BT, AT. If the letter indicating the impact resistance is not followed by the letter T, then the safety glasses should be used only against high speed particles at room temperature.

OPTIONAL REQUIREMENTS

The eyes are organs that provide coloured images of near, far, bright and dark objects.

The eye is externally covered by a membrane called sclera, that protects the most internal and delicate parts of the eye. In the front part of the eye the sclera is transparent and it is called cornea. Focused by the cornea, the light reaches the back of the eye called iris, which is a coloured part of the eye. It absorbs and controls the amount of light that enters into the eye, opening and closing the pupil, which is a dark circular opening at the centre of the iris. Then, the light reaches the eye’s crystalline lens, a flexible lens that can modify its thickness and its bending thanks to the eye muscles. This ability allows to focus objects at different distances. Retina is the last organ reached by light. It is the light-sensitive inner layer of the back of the eye. The retina, stimulated by the light reaching it, sends information as electrical signals to the brain through the optic nerve. The human eye is so one of the most delicate and complex human organs that, being exposed to various risks in work environment, has to be protected. For this reason, safety glasses have to be considered as P.P.E.. To protect the worker’s health and safety and to choose the right type of protection, it is important to know and classify these risks, which can be divided as follows:

	MECHANICAL RISKS High-speed particles, chips, metal powders, droplets and liquid splashes.
	CHEMICAL RISKS Mist, vapour and gas, liquid aerosols, fine dusts, splashes of chemicals.
	OPTICAL RADIATIONS RISKS Ultraviolet and infrared radiations, glare caused by high intensity light.

MECHANICAL RISKS

The protection against mechanical risks is recommended for all those manufacturing operations where there is a risk of accidental eye contact with high-speed objects or particles. Typical operations are: turning, milling, sandblast, riveting, grinding and other operations in which there are frequent projections of solid volatile particles (metal, stone, sand, wood) with a consequent impact at different speeds.

According to the impact extent, the hazards may be: lesion of the cornea, laceration of the iris, crystalline lens opacity, irritation, pain and conjunctivitis. It is necessary, then, to choose the appropriate eye protector in accordance with impact speed to which you can be subjected:

SYMBOL MARKING* (lenses and frame)	IMPACT		TYPE OF EYE PROTECTOR
	Impact level	Impact speed	Glasses	Goggles Masks	Face masks
F	Low energy impact	45 m/s (162 km/h) Steel ball with a diameter of 6 mm and a mass of 0,86 g
B	Medium energy impact	120 m/s (432 km/h) Steel ball with a diameter of 6 mm and a mass of 0,86 g	Not applicable
A	High energy impact	190 m/s (684 km/h) Steel ball with a diameter of 6 mm and a mass of 0,86 g	Not applicable	Not applicable

* If the symbol F, B or A is not found on both the lenses and the frame, then the lower value is assigned to the complete set of safety glasses.

CHEMICAL RISKS

Protection against chemical risks is recommended for some types of applications, such as handling of toxic dusts or corrosive liquids, which may represent a potential risk to the eyes of the operator. This risk may occur especially in the medical, agricultural and food fields or in waste management, where micro-organisms may contaminate the operator. The risks to which the operator may be exposed to are: conjunctivitis, ulceration of the cornea, viral infection and partial or total blindness.

It’s important to choose properly the suitable eye protector in compliance with the required protection:

SYMBOL/ MARKING* (frame)	PROTECTION AGAINST	TYPE OF EYE PROTECTOR
		Glasses	Goggles Masks	Face masks
3	Droplets of liquid	Not applicable		Not applicable
	Splashes of liquid	Not applicable	Not applicable
4	Dust particles of big dimensions (> 5 μm)	Not applicable		Not applicable
5	Gas and particles of fine dust (< 5 μm)	Not applicable		Not applicable

* If the frame of eye protector is not marked with none of the symbols 3, 4 and/or 5 the eye protector cannot be considered as suitable to protect against chemical risks.

OPTICAL RADIATIONS RISKS

Protection against this type of risk is provided by lenses or filters, that refer to appropriate European Standards such as: ultraviolet filters (EN 170), Solar Protection filters for industrial use (EN 172) and welding filters (EN 169). To understand the usefulness of these filters, it is appropriate to explain the basic principles: solar light is propagated through a beam of electromagnetic waves, of which only a part hits earth overcoming the ozone layer.

What we perceive is made up of:

• visible radiations (which compose the so-called “visible spectrum”): they are electromagnetic radiations with a wavelength between 380 and 750 nm; they are composed of the only rays visible to the human eye that materialize in the form of colours.

• ultraviolet radiations (UV): they are electromagnetic radiations with a wavelength between 100 and 380 nm. These rays are not visible to the human eye and they can be especially found in environments with the presence of solar light. Moreover, such radiations are harmful to humans because they are made up of magnetic waves which penetrate into the eye thus causing uncomfortable feelings and/or illnesses after a prolonged exposure (like it happens for the skin: little quantities of UV rays penetrate the skin causing tan, but prolonged exposure could be harmful to health). The risks connected to such radiations may be: lesion of the cornea, conjunctivitis, partial blindness, premature ageing of crystalline and cataract.

• infrared radiations (IR): they are electromagnetic radiations with a wavelength between 780 and 2.000 nm. These radiations are harmful to humans because they emit heat coming from all warm bodies (including the Sun, but even during welding or manufacturing of metals and glass). For this reason, the damages caused by such radiations are perceived in a nearly immediate way (unlike those caused by ultraviolet radiations which, on the other hand, appear later). Actually, we should consider that the ozone layer filters good part of IR rays of solar light which, therefore, come to us in a very restricted and not dangerous quantity; the rays we should defend from are those artificially created, resulting from incandescent materials. The risks connected to such radiations may be: crystalline lens opacity, cataract and partial blindness.

We can consider the following table, If we wish to list all kinds of risks, associating them with relative sources of danger to which we may be subjected in an industrial context:

The optical radiation commonly called “light” is made up of waves that oscillate in all directions of the threedimensional space, that is to say vertically, horizontally and along all the angles between these dimensions. When this light meets a reflective surface (water, ice, snow, sand, street surface) it undergoes a process called polarization, that is, it begins to move in a two-dimensional range (vertical and horizontal).

The vertical light brings a lot of useful information to the human eye, enabling colour vision and the perception of contrasts. The horizontal light (polarized light), on the contrary, creates optical noise, disturbing vision and generating the so-called reverberation or glare.

Polarized lenses aim at erasing just those annoying reflections that cause glare. They are, in fact, lenses with a “vertical structure” they absorb the horizontal light rays, responsible for glare, letting only the vertical rays pass, which are “useful” and rich of information.

Vision in bright light condition is greatly improved: natural colours, clear and clean vision even in the distance and less eye strain. Therefore, the use of polarized lenses allows to filter radiations selectively, without damaging any detail of the image. In the presence of bright light, in fact, they act as a “Venetian blind” which blocks unwanted rays, while in the absence of glare they behave exactly like traditional lenses.

VISION WITHOUT POLARIZED LENS	VISION WITH POLARIZED LENS

STANAG 2920 and STANAG 4296 are standards for the evaluation of ballistic resistance in all member countries of NATO. Unlike the compliance with the European Norm EN 166 which determines the impact resistance of a steel ball with a diameter of 6 mm and a mass of 0,86 g hitting the eyepieces at a speed of 45 m/s, the compliance with STANAG 4296 standard guarantees the ballistic resistance defined by STANAG 2920 standard, determining the ballistic resistance against bullets having a caliber of 3.6 mm (0,14″) and a weight of 325 mg, fired at a speed of 215 m/s, or 774 km/h (with the possibility of reaching even higher speeds as reported by the test report). STANAG 2920 does not define a minimum protection threshold in the same way as EN 166, but it allows to specify a speed V₅₀ that represents the speed at which a bullet could perforate the eyepiece with a 50% probability. In addition, glasses complying with STANAG 4296 standard must also meet a number of requirements, such as:

• impact resistance according to the conditions defined by STANAG 2920 standard;
• criteria about their use: the glasses must be as light and comfortable as possible, have a maximum fogging reduction (through ventilation and/or an appropriate coating) and have a good resistance to scratches in case of prolonged use;
• optical quality: glasses must provide a visual field of at least 160° and must not distort vision;
• additional features: the glasses must have a gloss level as low as possible and must be compatible with the use of other protective elements.