I've been googling, searching this community and looking over the 2017 NEC codebook (which can be very confusing) and I've come to the conclusion that a crystal clear, no nonsense, straight forward answer to this question doesn't exist. I don't know how, I must have overlooked it, but best I can tell, the information (in a very clear format) isn't out there. So could someone please help me out here? (sorry for the preface, I'm used to being accused of not doing research/making duplicate questions so I wanted to, more or less, show the steps I took before I decided to ask a question here).
AFCI breakers are
significantly more expensive than AFCI receptacles. (Scratch that, it's the GFCI breakers that are significantly more expensive than the receptacles...well regardless, I'm still curious about this and it would be good to know!) and I had the idea of installing an AFCI blank face outlet (which, I can't imagine what other use a blank face outlet would have honestly) right beside the breaker box before heading out to the circuit so that the entire circuit would be protected.
My idea was to buy a metal multi-gang box (or more) and mount them beside the breaker box, then run conduit to them (short runs) and have the circuit go through these boxes which will have blank face AFCI receptacles (one per each circuit)
The only crystal clear piece of information that I have though is that from the box, to the first receptacle, it must be armor clad cabling, or in metal conduit and the first box must be metal and grounded. This is where I get confused though because I've seen a couple of people state that every single box downstream of the AFCI receptacle must be metal also. I've seen that specifically mentioned, but I've also seen it omitted (only mentioning conduit to the first box and the first box being metal). Considering the entire reason for an AFCI in the first place, it makes sense that they require armor clad cabling or conduit up to the first AFCI protected receptacle, as well as that box being required to be metal. But I don't understand why every box downstream must be metal too since, for all intents and purposes, this receptacle would be acting exactly like an AFCI breaker, which I don't believe I've seen anybody say that device boxes and junction boxes must be metal on an AFCI breaker protected circuit.
I didn't see anything in the NEC code book though, that was very clear that all receptacles downstream must be in a metal box, but the way they word things can be a little confusing so I could have misread/misunderstood. So I'm wondering if maybe somebody just made that assumption and said that but it's not actually required?
My concern is not about being code compliant, but rather safety. Obviously I must be at least code compliant, but it's like it was stressed when I was driving a truck over the road; Be SAFE and legal. Safety ALWAYS comes before being legal.
Thank you kindly for your help!