European Standard EN 166 (specifications/housing and lens markings)
SAFETY GLASSES (SPECTACLES)
Impact resistance for mechanical strength F is tested using a ballistic test - firing a 6mm steel ball weighing 0.86g travelling at maximum 45 m/s at the time of impact.
mechanical strength S is tested by simply dropping a 43g 22mm steel ball onto the lens from a height of 15 inches.
Grade F is suited for tasks like drilling, sawing, grinding, hammering or risk from any process which could emit particles whose energy equates to the test specifications above.
Grade S can be used in hazardous areas where there is risk of small flying particles from other workers or processes in the vicinity but where the wearer is not close to the source of the hazard.
Housing has higher impact resistance with greater protection from hazardous liquids, dust and gases. Gasket on the rear forms a tight seal with the wearers skin.
Goggles provide the minimum protection with mechanical strength B (6mm 0.86g steel ball at max 120m/s on impact)
Housing has even higher impact resistance but offering head protection and prevents damage to soft tissues of the face. Often safety spectacles are worn beneath in addition.
Face shields provide protection with mechanical strength A (6mm 0.86g steel ball at max 190m/s on impact)
Welding Classes and recommended field of use (EN169)
See also links to....
Personal Protection at Work Regulations (2002)
HSE Short guide to PPE regulations 2002
Other relevant EN standards are...
EN 169, Personal eye-protection - Filters for welding and related techniques - Transmittance requirements and recommended use
EN 170, Personal eye-protection - Ultraviolet filters - Transmittance requirements and recommended use
EN 171, Personal eye-protection - Infrared filters - Transmittance requirements and recommended use
EN 172, Personal eye protection - Sun glare filters for industrial use
EN 175, Personal protection - Equipment for eye and face protection during welding and allied processes
EN 207, Personal eye-protection - Filters and eye-protectors against laser radiation (laser eye-protectors)
EN 208, Personal eye-protection - Eye-protectors for adjustment work on lasers and laser systems (laser adjustment eye-protectors)
EN 379, Personal eye-protection - Automatic welding filters
EN 1731, Personal eye protection - Mesh eye and face protector