# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/Da061uEPxp8
- **Gondola URL:** https://gondola.cc/posts/67970784-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/df995dd1f6.jpg
- **Posted:** 2026-07-15T20:26:52.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

Every safety poster tells you never to put water on an electrical fire. Watch a fireground crew do exactly that, whipping the nozzle side to side, and the reason lives in the geometry of the stream rather than the chemistry of the water.

Pure water is nearly an insulator — deionised water resists current at the megaohm scale. What leaves a hydrant is not pure. Dissolved iron, calcium and chloride ions turn it into a modest conductor, and a solid, unbroken stream aimed at energised equipment becomes a continuous wire back to the nozzle team. What decides whether that hurts you is current, not voltage. Perception starts near 1 mA; the muscles that let you release a grip lock up somewhere past 10 mA.

The defence is to destroy the continuity of that conductor:

- A fog pattern shatters the jet into droplets separated by air. Charge can no longer run along an unbroken column — it must arc gap to gap, and every air space piles on resistance. A 30-degree cone is the recommended attack pattern.
- Oscillating or whipping the nozzle chops the stream in time as well as space, so no single conductive thread ever bridges the equipment and the crew. Fast nozzle movement means current is seldom carried back unless the team is very close and the source sits above 600 V.
- Distance finishes the work. Even a solid stream breaks into droplets in flight; more air per metre means more resistance.

Underwriters Laboratories measured it. Nudging a solid jet to a 10-degree cone dropped the current below the threshold of feeling. At roughly six metres from a 1,000 V source, leakage fell under 2 mA — the accepted safe line. Salt water, far more conductive, is never used.

The stream that looks reckless is engineered to fail as a circuit.

#stemantics #firescience #electricalsafety #physics #engineering

## Stats

- **Views:** 80,667
- **Likes:** 549
- **Shares:** 0
- **Comments:** 21

## Tags

firescience, engineering, physics, electricalsafety, stemantics

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