What vinegar acidity is necessary to effectively kill household mold?

5% appears to be adequate per a brief search of the web.

30% is not really "vinegar" anymore - call it acetic acid and treat with care.

I have seen 10% sold as "cleaning vinegar" but I don't find any results in a quick search indicating it's much more effective than undiluted 5% on mold.

I've used white vinegar which runs about 7% and it's worked great for surface and below surface mold whereas bleach is only good for surface mold. if you've really got vinegar that's 30%, I'd handle with care and get rid of it.