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I have been preparing bleach disinfectant lately in a spray bottle and have been spraying on my couch, door mat, door knots, etc... I don't rinse it... So I assume there is bleach residue left after evaporation. Is it safe to leave the residue?

I felt some very mild burn like feeling on my arms when putting my arms on my couch lately; I don't know if this is some kind of placebo effect or if it is real.

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In the UK most bleach contains NaOH and NaClO. The hypochlorite (which is the bit that does the bleaching) breaks down to common salt and free oxygen. The hydroxide doesn't. So it's possible you are experiencing some kind of chemical burn.

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  • The hydroxide will "break down" (but possibly at a slower rate). It will react with carbon dioxide in the air and form sodium carbonate (a much weaker base than NaOH). A perhaps more well-known case is for calcium hydroxide (Ca(OH)2) used as lime paint, reacting to form calcium carbonate (Ca2CO3).
    – Peter Mortensen
    Mar 28, 2020 at 23:50
  • The NaOH they add to it is to prolong shelf life. And the reaction by which sodium hypochlorite is reduced to sodium chloride consumes protons, producing even more hydroxide, so it's indeed possible that residual alkali is causing the irritation the OP is describing. Reaction with CO2 is not incredibly fast. Same as for my comment above about the hypochlorite itself, I would recommend some caution with such effective but quite harsh chemicals.
    – user15121
    Mar 29, 2020 at 16:48
  • Thanks for the additional clarification. I'm new here :) And, this is not meant as a criticism of the OP, this is really a chemistry question, isn't it?
    – timpin
    Mar 30, 2020 at 4:10
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    ok thx for the replies but is the residue safe or not?
    – yeahman
    Mar 30, 2020 at 10:06
  • I have stopped spraying on the couch.. only on my door knots, light switches, sink, toilet and sink handles
    – yeahman
    Mar 30, 2020 at 10:06
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 In its manufacturing process, hypochlorite bleach begins as salt and water. After use, the compound breaks down mainly into salt and water during or quickly after use.

So it's table salt left behind, NaCl, as well as the similar NaClO3 and NaOCl.

https://www.infectioncontroltoday.com/environmental-hygiene/dispelling-myths-about-bleach-odors

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  • Is the effect the same if the applied bleach on a surface is not diluted in water? i.e. the compound would breaks down mainly into salt and water?
    – I likeThatMeow
    Mar 28, 2020 at 19:52
  • You can only buy diluted bleach, usually at 5%
    – Graham Chiu
    Mar 28, 2020 at 20:13
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    Yes, it's made from Salt sand decomposes to Salt
    – Graham Chiu
    Mar 28, 2020 at 20:59
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    As a chemist, I would not be so sure that bleach, diluted or not, decomposes so quickly after application to a surface. It depends on what it finds to react with and many other factors. I would definitely never use undiluted (3-6%) bleach on anything I don't rinse afterwards. And even with diluted bleach, I would let it react and wipe it off before resting on it. But by all means, it's my favourite disinfectant and I recommend it over anything else. Only, consider that it's so powerful precisely because it's so reactive. So, caution is advised.
    – user15121
    Mar 29, 2020 at 16:34
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    BTW, there are ways to test for residual bleach. Iodide+starch strips typically. They are sold online, or you can make them yourself if you can get hold of potassium or sodium iodide.
    – user15121
    Mar 29, 2020 at 16:38

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