Fire safety isn't usually the first thing homeowners think about when picking exterior paint colors, but it's one of the more consequential tests a coating can undergo — and one most people never think to ask about at all. This week's Fact Check Friday breaks down the surface burning test behind Rhino Shield's Class A fire rating.
What the Lab Actually Tested
Commercial Testing Company, based in Dalton, Georgia, ran ASTM E84-21a on the Rhino Shield coating system — primer plus finish coat — applied to fiber-reinforced cement board at the recommended thickness. This is the standard test method for surface burning characteristics of building materials, more commonly known as the Steiner tunnel test, and it's the same ASTM standard used by code officials nationwide (it's the technical equivalent of UL 723) to rate how materials perform when exposed to flame and heat.
The test exposes a 24-foot-long specimen to a controlled flame at one end and measures two things over a 10-minute period: how far the flame travels across the surface (Flame Spread Index) and how much smoke the material produces (Smoke-Developed Index). Both are scored relative to two reference materials — red oak flooring, which is arbitrarily set at 100, and fiber-reinforced cement board, set at 0.
The Rhino Shield coating system scored a Flame Spread Index of 5 and a Smoke-Developed Index of 0. Surface flame spread during testing reached a maximum of just 1.45 feet beyond the ignition point, at a peak recorded temperature of 581°F.
What "Class A" Actually Means
The National Fire Protection Association's Life Safety Code (NFPA 101) classifies surface burning results into three tiers: Class A covers anything from 0 to 25 on the Flame Spread Index, Class B covers 26 to 75, and Class C covers 76 to 200. A score of 5 puts Rhino Shield firmly and comfortably in Class A — the same classification tier required for interior finishes in many commercial buildings, schools, and healthcare facilities where fire code standards are strictest.
The Smoke-Developed Index matters just as much in a real fire scenario, since smoke inhalation is a leading cause of fire-related injury and property loss, often before flame itself becomes the primary danger. A score of 0 means the coating contributed effectively no smoke development during testing.
Why This Is Worth Knowing Before You Repaint
Most exterior coatings on the market have never been put through ASTM E84 testing at all, simply because it isn't required for a residential repaint. That means most homeowners have no way to compare fire performance between products — the information just isn't published. We think it should be, especially for a coating system designed to last decades on your home rather than get replaced every 5–7 years.
A Class A rating doesn't make a home fireproof, and no coating can promise that. What it does mean is that in the event of exterior fire exposure — from a grill accident, a neighboring structure, or dry-season brush — the coating itself isn't accelerating flame spread or generating significant smoke, which can matter for both safety and, in some cases, insurance considerations.
Download the complete Rhino Shield Testing Book (PDF) — the full E84 report and every other test in this series, straight from the independent labs: https://irp.cdn-website.com/ceae3fe7/files/uploaded/RhinoShield_TestingReportDoc_R3-1.pdf
Curious what a Class A-rated coating system looks like on your specific home? Request a free estimate or call (630) 984-4440.
