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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?
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 |
As a basic material Polycarbonate also offers the best basic protection against heat. It has a Heat Distortion Value of 265º F, while Propionate has a value of 162º F and Acetate 163º F. However further heat resistance can be achieved with for instance Silver and Gold coatings 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. Silver coated shields can provide protection up to 1,400º F. Gold coated shields can protect against radiant temperatures up to 1,800º 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 |
| 265º F |
265 |
||
| 225 | |||
| 200 | |||
| 175 |
162 |
163 |
|
| 150 | |||
| 125 | |||
| 100 | |||
| 75 |
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.
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!
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.
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).
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.
Face shields are tested to ANSI Z87.1-2003, and below you will find a summary of the Requirements and Test Procedures.
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" |
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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