- Aluminum RMC and its associated fittings are fine where installed per Sections 344.10(A)(3) and (B)(2).
- They must be listed per Section 344.6 but NOT specifically for Classified Locations.
- Section 501.10(A)(1)(a) and by back reference in Section 501.10(B)(1)(1) specifically permit various forms of RMC and their associated fittings in Classified Locations.
- Class I, Division 1 boxes and fittings must comply with Section 501.10(A)(3).
- Class I, Division 2 boxes and fittings only need to comply with Section 501.10(B)(4) with a few limitations as noted previously.
- Section 500.8(C)(6)(a) does not require boxes and fittings to be specifically marked for Classified Locations.
Your Aluminum LB is fine in the application as described.
That should cover the OP.
Robert B. Alexander, P.E.
Answers based on 2014 NEC unless otherwise noted.