--- title: "Express Inhibitor Test Purpose" description: "The Fernox Express Inhibitor Test tells installers in seconds whether a heating system holds enough corrosion inhibitor, and the Fernox App turns that reading into a documented report before they leave site." url: https://help.fernox.app/en/articles/126-express-inhibitor-test-purpose collection: "Express Inhibitor Test" updated: 2026-11-05 language: en alternates: [de, es, fr, cs, fr-be, nl-be, nl, sv, ro, pl, sk, tr] --- # Express Inhibitor Test Purpose The Fernox Express Inhibitor Test tells installers in seconds whether a heating system holds enough corrosion inhibitor, and the Fernox App turns that reading into a documented report before they leave site. ## Why inhibitor levels matter Inhibitor protects a heating system from the inside. It slows the corrosion that turns metal into sludge, which blocks radiators, reduces efficiency and shortens boiler life. But inhibitor levels drop over time through leaks, top-ups with fresh water and system work. That's why checking the level matters, not just adding inhibitor at installation. The Express Inhibitor Test gives a simple pass or fail on the spot, so you know the system is protected and can prove it. ## What's in the kit and how it works The [Express Inhibitor Test](https://fernox.com/residential-solutions/express-inhibitor-test/) is a pot of 50 test strips, one strip per system. Each pot has a colour chart on its pot The strips measure molybdate, the active ingredient in most inhibitors. That means the test works with all Fernox Protectors, including Protector F1, and with any other molybdate-based inhibitor.

Chemical Fields	Express Inhibitor Test
Turbidity	✕
Corrosion	✕
pH	✕
Molybdate (mg/L)	✓

## If the test fails A fail means the system doesn't hold enough inhibitor. You can fix it on the same visit: dose the system with more inhibitor, let it circulate, then retest and issue a passing report. There's no need to come back another day. ## Compliance and warranties Testing inhibitor concentration helps you comply with BS 7593:2019, the UK code of practice for treating water in heating systems, and the Benchmark scheme. Many boiler manufacturers also need proof of correct water treatment to keep the warranty valid, and the PDF report provides it.