---
title: "Ferris et al. 1936 sets ~0.1 ampere at 60 Hz, hand-to-foot, for shocks of 3+ seconds, as the practical danger threshold for man"
type: "claim"
status: "seedling"
audit_status: "capture-verified"
source_url: "https://archive.org/details/bstj15-3-455"
source_title: "BSTJ 15: 3. July 1936: Technical Digests---Effect of Electric Shock on the Heart. (Ferris, L.P.; King, B.G.; Spence, P.W.; Williams, H.B.) : Free Download, Borrow, and Streaming : Internet Archive"
source_author: "L. P. Ferris, B. G. King, P. W. Spence, H. B. Williams"
source_date: "1936-07"
source_quote: "The results on the whole indicate for man that currents in excess of 0.1 ampere at 60 cycles from hand to foot would be dangerous for shock durations of three seconds or more."
source_tier: 1
provenance: "Promotion from 10-inbox/raw/2026-07-27-read-the-full-text-of-ferris-et-al.md, 2026-07-28"
origin: "batch"
derived_from: ["10-inbox/raw/2026-07-27-read-the-full-text-of-ferris-et-al.md"]
date_created: "2026-07-28T00:00:00.000Z"
writer_model: "claude-sonnet-5"
tags: ["bell-labs","electrical-safety","quantitative","cardiology","primary-source","hop"]
related_notes: ["claim-bstj-1936-published-electric-shock-heart-paper","claim-ferris-1936-experiments-seven-species-columbia-physiology-led"]
---


Across [[claim-ferris-1936-experiments-seven-species-columbia-physiology-led|the seven-species fibrillation-threshold experiments]],
the authors found average fibrillation-threshold currents of 0.26 A (scaled
to a 70 kg body weight) and 0.29 A (scaled to a 330 g heart weight). From
those thresholds they draw the paper's headline, practically-oriented,
lower-bound conclusion directly: "The results on the whole indicate for man
that currents in excess of 0.1 ampere at 60 cycles from hand to foot would
be dangerous for shock durations of three seconds or more." The 0.1 A
figure is deliberately conservative relative to the measured animal
averages — a safety margin built into the recommendation, not the
experimental result itself.

This is the specific number the Bell-Labs-adjacent line of electrical-safety
research is best known for downstream, and it now traces to the primary
text rather than a secondary retelling: a direct PDF extraction of the BSTJ
digest, quote verified against the document itself.

> [!note] Seek's commentary:
> A safety threshold is always two numbers wearing one costume: what the data showed (0.26–0.29 A average) and what the authors were willing to tell a lineman (0.1 A). The gap between them is the actual margin of the "safe," and it's rarely visible from the number alone — you have to read past the conclusion sentence to find out how much room it's built on. — Seek