Download Safety Glasses versus Safety Goggles

Safety Glasses versus Safety Goggles
In the research laboratory, properly fitting safety glasses (with eye shields)
are the minimum level of eye protection permitted. Every laboratory worker should
have his or her own pair of safety glasses, prescription if necessary. They should
also have a pair of properly fitting chemical splash goggles as well. Of these safety
devices needs to be inspected and cleaned regularly to be effective—dirty glasses or
goggles hinder eyesight, badly fitting ones will not protect as well from splash.
Safety glasses are appropriate for many laboratory techniques, but certainly
not for all. The main criterion for deciding whether safety glasses are sufficient or if
the more protective chemical splash goggles are the appropriate eye safety device
is: what is the chance that something would be splashed in the eye and what would
the consequences of that contact be. If the chance of something being splash or
sprayed into the eye is high, or if the reagent is highly corrosive or poisonous,
chemical splash goggles are required.
As an example of a common laboratory procedure, thin layer
chromatography would normally be a good example of a technique where safety
glasses are sufficient: ordinary solvents in relatively small quantities, and silica on
glass or polyester backing. But if the plates are to be developed by spraying
ninhydrin on potassium permanganate solutions onto them, splash goggles must be
worn. There is a high chance that the reagent might inadvertently get into the eye
(even if done in a hood) and the reagent itself would be highly damaging to ocular
tissue.
Working with corrosive acids (or bases) is another common procedure.
While small quantities of dilute acids can be appropriately used with just safety
glasses (10 mL of 1 M HCl for example), any manipulation of concentrated acids (all
solutions above 6M in strength at a minimum) require splash goggles. If more than
2.5 L of the full strength acids (18 M sulfuric for example) a face shield in addition to
the splash goggles is required. Of course an appropriate lab coat and gloves need to
be worn as well, but they are beyond the topic of this discussion.
Cleaning glassware is another example where safety glasses are normally
sufficient. However once the cleaning agent becomes something more powerful than
the ordinary surfactant cleaning solutions, splash goggles are needed. Using
potassium hydroxide/ethanol base baths and chromic-sulfuric acid baths are both
examples where chemical slash goggles are definitely required.