It is likely from ArcWear test experience that a face-shield/balaclava (called a hood in the OSHA standard) would be OK up to about 20 cal if properly designed and rated (NFPA 70E cuts them off at 12 cal but this is based on data without use of safety glasses under the shield) but at some point you should move to a more thorough protection like a balaclava/goggle (if you have low risk of shrapnel) or a bee-keeper’s style hood if there is more risk of shrapnel to the face. Most of the shrapnel we have seen in arc flashes has been porcelain from insulators and switch gear. Often trainers refer to molten metal particles at 700 MPH as “shrapnel”, these materials will not go through a cloth and enter the body so a face-shield is not the issue. We have no deaths related to arc flash “shrapnel” on record so focus on protection and comfort. Some new hoods like the Salisbury lift front hood are more like a face shield. The user has a little more freedom in the OSHA standard but only tested and rated systems should be used.
By the NFPA 70E definition, a balaclava is part of an arc flash suit or flash suit hood because it helps provide 360 protection. If you use the tables, you must use a bee-keeper’s style hood with a face piece but if you have done calculations, you may use a balaclava/goggle or balaclava/face-shield to higher levels than allowed by the tables (see Annex H.3).
Two pros of using a balaclava/goggle as an arc flash hood:
Two cons of using a balaclava/goggle as an arc flash hood: