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Chapter 10: Acids and alkalis · Part 2: Acids

Hydrochloric acid

  • Poison schedule (Australia)
  • Contaminant risk
Also called
muriatic acid, pool acid
Found in
toilet cleaners, scale and rust removers, brick and concrete cleaners, pool acid

The worst fact: a woman died 29 hours after swallowing 60 mL of 35% hydrochloric acid. In NSW in 2014–15, 54.5% of Poisons Information Centre callers about hydrochloric acid (not pool acid) were already in hospital or were referred there. A 10% solution caused permanent eye damage in rabbit tests.

Why brands use it: it's a cheap, strong acid that dissolves scale, rust and cement fast.

Take care if: you also use bleach or pool chlorine: together they make chlorine gas. In the US, nine people went to hospital after pool acid was mixed with a chlorinator. Never use it on marble, limestone or lime mortar. In Australia it's a Schedule 5 Poison above 0.5% and a Schedule 6 Poison above 10%.

Comes from: about 90% is a by-product of making other chemicals, including chlorinated solvents and vinyl chloride for PVC plastic. Some of the rest is made by burning hydrogen in chlorine.

Myth check: nil.

Contaminants: chlorinated hydrocarbons. By-product acid can carry traces of the solvents it came from. They're unlikely in a well-made product, but it's a factor you can't see on the label.

Fair to say: your stomach makes it too, and in the US it's an approved food additive. The danger is strength.

Correct as of November 2026. What the badges mean

Sources

  • Australian Government. Poisons Standard October 2026 (SUSMP), F2026L01327: sodium hydroxide, potassium hydroxide, alkaline salts, monoethanolamine, sulfamic acid, hydrochloric acid, acetic acid; Appendix B (sodium bicarbonate).
  • Safe Work Australia. Hazardous Chemical Information System (HCIS): classifications for each chemical, and for ethylene oxide, carbon monoxide and acetaldehyde.
  • AICIS / NICNAS. IMAP assessments: soluble silicates; ethanolamine (2013); hydrochloric acid (Tier II 2014, Tier III 2018); acetic acid (2013).
  • ACCC. Analysis of consumer product related calls to the NSW Poisons Information Centre, June 2014 to May 2015 (2016).
  • US EPA. Chemical Safety Alert: safe storage and handling of swimming pool chemicals (2001); Federal Register 74:26692 (L-lactic acid, 2009).
  • HSDB (US National Library of Medicine), via PubChem: production and impurity data for each chemical.

The full source list is at the end of Chapter 10.