Q: Are these [paragraphs] separate or can they be used together?
(C) Arc-rated protection is not necessary for the employee’s head when the employee is wearing head protection meeting § 1910.135 if the estimated incident energy is less than 9 cal/cm2 for exposures involving single-phase arcs in open air or 5 cal/cm2 for other exposures,
(E) For exposures involving single-phase arcs in open air, the arc rating for the employee’s head and face protection may be 4 cal/cm2 less than the estimated incident energy.
For example, if we have estimated the incident energy at 12.99cal/cm2 for single-phase open air, then we reduce this value to 8.99 cal/cm2 from E above and thus no face shield is needed as long as the hardhat meets 1910.135 from C above. Or is C derived from E?
Don’t think that is the intention. The idea behind both of these phrases is to keep from overburdening climbing line workers from having restrictive PPE when possible. Paragraph E assumes you will be wearing a shield but allows you to avoid a HOOD rather than making the 9 cal cut-off be a 12 cal cut-off.