When working in the lab, it is important to ensure that your students’ eyes are protected. But how much protection is necessary, and under what circumstances should you use which type of eyewear? This post will help you determine what’s right for your classroom based on the environment in which they’re used.
All safety glasses are required by the American National Standards Institute (ANSI) to resist the impact of a quarter-inch steel ball striking at 150-ft/s, so you can be sure that certified safety glasses will protect your students’ eyes from any projectile in the lab! Safety glasses can be used while cleaning glassware, in the presence of wood or metal particles, or where small quantities of dilute acid are being utilized (such as a few milliliters of 1-M HCl).
While safety glasses serve these purposes well, they tend to have minimal side-shields and are open at both the top and bottom. Therefore, they are not suited to working with more concentrated chemicals, or those that emit fumes; they are the minimum level of protection required in lab.
On the other hand, safety goggles provide more coverage: 360-degree protection around the eyes with an elasticized strap to ensure a good seal. They are best utilized in the presence of more concentrated chemicals, increased heat, and minimal fumes. The seal, while important for protection, means that the inside of the goggles may fog. This dichotomy is resolved differently by each of the three kinds of goggles.
Direct ventilation goggles have vents that face forward; their main purpose is to prevent projectiles from entering the goggles. ANSI dictates that these vents not admit particles 1.5 mm or larger. There is little risk of fogging in these goggles, but they are only to be used when solid projectiles are the main danger, rather than chemical splashes.
Indirect ventilation goggles have angled vents, so that projectiles coming straight at the viewer will not enter the goggles. This sort of ventilation is ideal for working with chemicals, as well as plating or degreasing.
No vent, or closed goggles, have no openings to admit the flow of air around the eyes, and are ideal for protection from chemical splashes or ultra-fine dust and debris. Since no vent goggles run a high risk of fogging, an anti-fog coating is applied to both the inside and outside of the lenses. These should be inspected regularly by the instructor to ensure that the coating is intact and will not obstruct the view of the student experimenter.
There are also goggles that have direct or indirect venting systems that can be sealed with a turn of the hand on the side of the goggles. These are a good purchase for a school system that can only afford to choose one type of safety eyewear. It is especially important to ensure that the anti-fog coating on these sorts of goggles is exemplary, because the manufacturer may neglect it if the goggles are considered multi-purpose.
Face Shields and Fume Hoods
Wherever you are working on a lab with high splash hazards, explosions, or full-strength acid (18-M), you should employ your fume hood and a face shield. While face shields may appear cumbersome, they tend to be lightweight and easy to wear. Generally anything that requires a face shield or a fume hood should be performed with the assistance of the instructor, or as a demonstration.
By understanding the different varieties of eye protection available, you can ensure that you and your students are safe as you explore together.