Editing Retrobrite (section)

== Peroxide concentrations and what they mean ==

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! Concentration !! Where you meet it !! CLP classification at that strength<ref name="clp" />
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| '''3 %''' || Pharmacy hydrogen peroxide solution || Eye Irrit. 2 (H319) from 5 %; below that, not classified for eye effects
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| '''6 % (20 volume)''' || Salon developer || Eye Irrit. 2 (H319) — the 5 % to 8 % band. The step up to serious eye damage happens at 8 %
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| '''9 % (30 volume)''' || Salon developer || '''Eye Dam. 1 (H318) — causes serious eye damage'''
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| '''12 % (40 volume)''' || Salon developer cream; the usual Retrobrite strength || '''Eye Dam. 1 (H318) — causes serious eye damage.''' 12 % is also the '''legal maximum''' for hydrogen peroxide present or released in a hair product under the cosmetics regulation<ref name="cosmetics">Regulation (EC) No 1223/2009 on cosmetic products, Annex III, entry 12 (hydrogen peroxide and other compounds or mixtures that release hydrogen peroxide), retained in GB law. Hair products: maximum 12 % H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; (40 volumes), present or released. Cited for the 12 % / 40 volume ceiling on consumer hair products, which is why salon developer does not go above that strength.</ref>
|-
| '''30–35 %''' || Laboratory chemical; sometimes sold for "vapour chamber" methods || '''Skin Irrit. 2 (H315)''' from 35 %, '''Eye Dam. 1 (H318)''', '''STOT SE 3 (H335)''' from 35 %. Acutely toxic if swallowed or inhaled (H302, H332)
|-
| '''50 % and above''' || Industrial || '''Oxidising liquid (H272)''', '''Skin Corr. 1B (H314)''' — severe skin burns. From 70 %: Ox. Liq. 1 (H271) and Skin Corr. 1A
|}

'''The "volume" scale on salon products is the oxygen volume, not a percentage.''' 40 volume is 12 % w/v, 30 volume is 9 %, 20 volume is 6 %. A bottle labelled only "40 vol" is the strongest hydrogen peroxide you can buy without a laboratory account, and the cosmetics regulation is the reason it stops there.<ref name="cosmetics" />