How long can you leave on the self? Hypochlorous Acid (HOCl) Shelf Life — And Why Freshness Matters Hypochlorous acid (HOCl) is one of the most effective, safe and versatile sanitising solutions available. But unlike many traditional chemical sanitisers, its performance depends on something a little more subtle than concentration. The real story sits in the chemistry—and the stability of that chemistry over time. It’s Not Just About ppm HOCl strength isn’t simply about how mu