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:
High-speed particles, chips, metal powders, droplets and liquid splashes.
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: glasses for low energy impact “F”, that is to say with impact velocity up to 45 m/s (100,6 mph), and the mid energy safety goggles “B”, that is to say with impact velocity up to 120 m/s (268,4 mph).
Ultraviolet and infrared radiations, glare caused by high intensity light.
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 nanometres; 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.
Mist, vapour and gas, liquid aerosols, fine dusts, splashes of chemicals.
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.