Notes on verification

Confirmed by peer-reviewed history (Spelce et al. 2018), CDC/NIOSH historical documents, and an independent LLNL/OSTI technical report citing Held 1978. Sources share a common historical lineage but no contradicting evidence found. [tier=silver indep_score=0.77 clusters=2 claim_tier=notable | framework convergence=partial on Historical accounts of USBM respirator approval program, largely tracing to Bruce Held's 1974/1978 history and the Spelce et al. peer-reviewed article series (upstreams: Bruce J. Held, 'History of Respiratory Protective Devices in the U.S.' (1974/1978, Lawrence Livermore Laboratory), Spelce et al., 'History of U.S. Respirator Approval' (J Int Soc Respir Prot, 2018-2020 series), USBM Schedule 13 (5 March 1919)) — publishers independent, evidence may not be | kind=empirical eligibility=high]