FAQ Face Protection

Can you tell me the pros and cons of different face shield materials?
Are all Polycarbonates the same?
What is the difference between a molded and a die cut face shield?
How do I select the right face shield for my environment?
What face shield material is best for impact protection?
What type of face shield material is best for chemical protection?
What is an ARC Flash?
What is the cause of an ARC Flash?
How can the ARC Flash risk be minimized?
What type of face shields should I choose for electric arc protection?
What type of face shields should I use in heat applications?
How are face shields tested?
Does OSHA approve face shields?

Can you tell me the pros and cons of different face shield materials?

The pros and cons will vary somewhat with the work environment and risk factors that you are exposed to. Do you need protection from Impact, Heat, Radiation or Chemical splash?

Impact:

Different face shield materials provide different levels of impact protection, but Polycarbonate currently offers the highest level of impact protection. It offers an Izod (ASTM D256) Impact Value of 18, while Propionate has an Izod Value of 10 and Acetate a Value of 3.5. These numbers provide you with the relative strength of these materials.

Table below shows relative impact resistance for select face shield materials.

Izod Impact Value	Lexan Polycarbonate	Propionate	Acetate
20
18	18
16
14
12
10		10
8
6
4			3.5
2

Link to description of plastic material test methods

Heat:

As a basic material Polycarbonate also offers the best basic protection against heat. It has a Heat Distortion Value of 265° F, while Propionate has a value of 162° F and Acetate 163° F. However further heat resistance can be achieved with Gold coating on top of the basic face shield material. These advanced face shields are used as protection against radiant heat in furnaces and metal and glass melting operations. Gold coated shields can protect against radiant temperatures up to 1,800° F. No absolute heat tolerance can be provided for radiant heat.

Table below shows heat distortion temperature for select face shield materials.

Temperature	Lexan Polycarbonate	Propionate	Acetate
265° F	265
225
200
175		162	163
150
125
100
75

Cold temperature properties:

Polycarbonate has a flexural yield strength of 13,500 PSI compared to only 5100 PSI for propionate. Flexural strength of a material is defined as its ability to resist deformation under load. The test method for measuring flexural strength is in accordance with the ASTM D790. Polycarbonate's brittle temperature is -277 degrees F. We have not found information about the brittle temperature of Propionate, but we have have had reports of Propionate shields breaking during cold weather use.

Radiation

Radiation can be simply sun glare or bright lighting conditions, or it can be welding, laser light or electric arc exposure. Special absorbers added to the face shield material can add protection against most of these dangers. For more information about this aspect, see Elvex face shield selection chart.

Chemical splash:

There are two aspects of chemical splash protection. First of all we want to protect the user from the chemicals in question. Second, users are concerned that the face shield hold up to miscellaneous chemicals, such as acids and strong alkali. All plastic face shields have a limited resistance to these chemicals, and there are no easy answers in regards to chemical resistance. It is usually a matter of how soon the material will be affected by a certain chemical, rather than if. Elvex offers select models of face shields that are hard-coated for improved chemical resistance. However, the hard-coatings do not hold up against aggressive acids and alkali.

Remember to always use safety glasses or goggles in order to protect your eyes, even when you use face protection. ANSI Z87 specifically requires this!

Are all Polycarbonates the same?

There are many brands and variations on Polycarbonate. There are polycarbonates that offer full UV protection (180-380 nm) and there are polycarbonates that do not. There are Polycarbonates that have higher heat resistance, and Elvex uses a high heat resistant Bayer Polycarbonate in our gold coated face shield (FS-18GL). This version has about 50 degrees F higher heat melting/distortion point. Our new generation of electric arc face shields (coming on line soon) are using a high meltflow Polycarbonate, allowing the chemical absorbers to be integrated during the molding process.

Elvex uses several brands of Polycarbonate for our face shields. Brands: Shields with a suffix "L" (such as FS-15L) are made from General Electric LEXAN, while our gold coated shields (FS-18GL) use a BAYER Polycarbonate, and face shields marked "PC" are made from a generic Polycarbonate that provides 99.9% UV protection. Shields marked with P are die cut from sheet Polycarbonate (such as FS-15P).

What is the difference between a molded and a die cut face shield?

Molded face shields are manufactured by injecting the plastic material under high temperature and pressure into a mold. Injection molded shields can be molded with a built in curvature and have a smooth edge. Generally molded face shield have a higher quality appearance.

Die cut face shields are cut with a die from flat stock material. From a performance standpoint the die cut shields perform as well as the molded shields. However, die cut shields are usually manufactured flat (as opposed to curved) and have to be bent into shape to fit into the headgear. Die cut shields can be formed in a separate manufacturing step. The die cutting process often leaves rough edges on the face shields, which creates the appearance of a less finished product. This can be overcome by edging the face shield with an aluminum border.

Both injection molded and die cut shields can be manufactured in different thickness, and can be manufactured with different coloration and absorbers.

How do I select the right face shield for my environment?

The first criteria is to select a face shield that is right for your environment. It has to provide the protection that you need in your environment. Read the fist question "Can you tell me the pros and cons of different face shield materials?" in order to help make this determination. Next you need to determine if an expensive shield will hold up longer or provide better work situation. You may find that an inexpensive die cut face shield that is replaced several times per week is a less expensive solution than a more expensive molded face shield that is replaced once a week. This could apply in a situation when you chose between a hard coated molded shield (example FS-18CL) and an inexpensive die cut shield (example FS-15P).

What is an ARC Flash?

It is a short circuit resulting in electrical discharge that uses the air as a conductor. The process ionizes air which then becomes almost as conductive as metal. This sudden and massive release of energy is like an explosion generating temperatures reaching up to 20,000 degrees C (35,000 deg F) which is 4 times hotter than the surface of the sun. This enormous energy can melt or even vaporize metal and other components blasting them with explosively hot gasses into the immediate region, destroying the electrical equipment involved and cause injury to persons working in the immediate vicinity.

What is the cause of an ARC Flash?

Generally confined to electrical systems greater than 480 volts, components such as switches, conductor terminations, fuses, circuit breakers, relay contacts, phase bus bars and such can become faulty through contamination by moisture, dust, corrosion or accidental contact through dropped tools. It is usually industrial electricians working on installations or repairing appliances who are in danger of being exposed to an arc flash.

How can the ARC Flash risk be minimized?

NPFA70e and IEEE 1584 detail guidelines and safe working practices designed to minimise the occurrence of Arc Flashes. These standards also discuss the various hazard categories grouped by the potential energy release expressed in terms of calories per cm² (or Cals) and list the appropriate Personal Protective Equipment (PPE) to be worn during certain work exercises. They also discuss workplace hazard risk assessments and methods to calculate the potential force of an arc blast.

What type of face shields should I choose for electric arc protection?

Electrical workers, linesmen and electricians working with high voltage connections are sometimes exposed to the sudden release of energy that occurs during an electrical arc. This is a very dangerous condition, that can result in serious burns and death. There has long been requirements established for safety clothing to be used by these workers, but from January 1, 2003, it is required that electrical workers use face protection meeting similar requirements. The National Fire Protection Association's standard 70E-2000 establishes Hazard or Risk categories, as shown in the table below. Elvex ARC-Shields are suitable for use in hazard/risk categories 1 and 2. The minimum Arc Thermal Performance Value (ATPV) has been established to be 5 cal/cm² and 8 cal/cm² for these two risk categories. (Cal/cm² stands for calories per square centimeter). Click on this link to read more about Elvex ARC-Shields.

How are face shields tested?

Face shields are tested to ANSI Z87.1-2010, and below you will find a summary of the Requirements and Test Procedures.

Test Performed	Description
High Mass Impact	Frame shall be capable of resisting impact from a pointed projectile weighing 500g (17.6 oz.) dropped from a height of 127 cm (50 in.).
High Velocity Impact	Face shields shall be capable of resisting impact from a 6.35 mm (1/4 in) diameter steel ball traveling at a velocity of 91.44 mps (300 fps). Goggles shall be capable of resisting impact from a 6.35 mm (1/4 in) diameter steel ball traveling at a velocity of 76.2 mps (250 fps). Spectacles shall be capable of resisting impact from a 6.35 mm (1/4 in) diameter steel ball traveling at a velocity of 45.7 mps (150 fps). For sample size of 6, no failure may occur (Z87.1-2003 required 20).
Drop-Ball Impact	Basic impact requirement for all devices: 1 inch diameter steel ball dropped at 127 cm (50 inches)
Coverage	Required lateral (side) coverage has been increased, and it is now the same as CSA Z94.03-02. No openings greater that 1.5 mm (0.06").
Penetration Test (Plastic lenses only)	Spectacles shall be capable of resisting penetration from a weighted projectile weighing 44.2 g (1.56 oz dropped from a height of 127 cm (50 in).
Prismatic Power	The prismatic power shall not exceed 1/2 prism diopter in any direction. Vertical and horizontal prism imbalance shall not exceed 1/4 prism diopter....
Refractive Power and Astigmatism	No requirement for face shields
Haze	Lenses shall not exhibit more than 3% haze, when tested in accordance with....
Optical Quality	No striae, bubbles, waves or other visible defects that would impair optical quality is allowed.
Transmittance	Clear and filter plano lenses shall comply with table 9 or 10 of Z87.1. Special purpose lenses shall comply with Table 7 through 10.
Cleanability	After cleaning the function of the spectacles shall not be impaired.
Optional Tests	There are optional tests for Welding lenses, UV lenses, IR lenses and VLT filters. For goggles optional tests include Splash/Droplet, Dust and Fine dust.
Markings	Impact protector (must meet High mass Impact, High Velocity Impact and Penetration tests) shall be marked Z87+ Non Impact Protector (must meet all requirements, except impact requirements) shall be marked Z87. Lens: Manufacturers mark, and if applicable "S" for lenses with less than 85% visible light transmission. Frame components: All major components shall bear Manufacturers mark and shall be marked "Z87" Optional tests and markings: There are optional tests for Welding lenses, UV lenses, IR lenses and VLT filters. If these properties are claimed, the have to be marked on the lens. Welding: W-followed by shade number UV filter: U and scale number Visible light filter: L and scale number IR filter: R and scale number Goggles only: Splash/Droplet: D3 Dust: D4 Fine Dust: D5
Criteria	Requirement
Minimum Thickness	1.0 mm (.039 in) at thinnest point
High Mass Impact	Face shield shall be capable of resisting impact from a pointed projectile weighing 500g (17.6 oz.) dropped from a height of 127 cm (50 in.).
High Velocity Impact	Face shield shall be capable of resisting impact from a 6.35 mm (1/4 in) diameter steel ball traveling at a velocity of 91.4 mps (300 fps). For sample size of 20, no failure may occur.
Drop-Ball Impact	Basic impact requirement for all devices: 1 inch diameter steel ball weighing 86 g (2.4 oz) dropped at 127 cm (50 inches)
Penetration Test	Face shield shall be capable of resisting penetration from a weighted projectile weighing 44.2 g (1.56 oz) dropped from a height of 127 cm (50 in).
Prismatic Power	The prismatic power shall not exceed 0.37 prism diopter in any direction. Vertical and horizontal prism imbalance shall not exceed 1/4 prism diopter and horizontal prism imbalance shall not exceed 0.125 diopter "base in" or 0.75 diopter "base out".
Refractive Power and Astigmatism	No requirement
Haze	Lenses shall not exhibit more than 3% haze, when tested in accordance with....
Optical Quality	No striae, bubbles, waves or other visible defects that would impair optical quality is allowed.
Transmittance	Clear and filter plano lenses shall comply with table one of Z87.1. Special purpose lenses shall comply with Table 2.
Cleanability	After cleaning the function of the face shield shall not be impaired.
Markings	Lens: Manufacturers mark, and if applicable "S" for lenses with less than 85% visible light transmission. All major components shall bear Manufacturers mark and shall be marked "Z87"

Does OSHA approve face shields?

No, OSHA does not approve face shields or any other safety product. OSHA requires manufacturers and users to comply with certain ANSI standards, and general OSHA guidelines.

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