While two solar modules can carry the same Class A designation, they can differ in their fire performance. The shared label can conceal differences that matter for the safety of the building below.

Class A is a defined classification reached through prescribed test criteria, and any Class A claim must identify the standard used. It should not automatically be interpreted as “fireproof”, nor does the classification itself tell a potential user how far beyond the pass threshold a particular solar module performed.

The first distinction is what the test measures: resistance to an external fire or the product’s contribution to fire development.

Under UL 790, Class A describes performance under severe external fire exposure. It does not classify the module’s materials as non-combustible.

European standards assess a product’s contribution to fire development under EN 13501-1 and a roof’s response to external fire under EN 13501-5. UL 790 Class A does not establish compliance with either; each requires separate evidence.

Even under UL 790, flames can spread farther across one module than another and both still pass Class A. Buyers need measured test results to compare them. A “pass” alone does not show how close either came to the limit.

Fire-resistant glass is only part of the design

A claim about fire-resistant glass says little about how the complete solar PV module behaves. The encapsulation beneath it can contribute to fire development, so flame-retardant materials also have a role in limiting fire propagation. Electrical faults create ignition risks that the glass does not prevent.

Cell-level current management can limit hot spots under shading, and reinforced electrical connections can reduce fault and arcing risks. A complete assessment of module fire safety must therefore examine both its response to external fire and the design features that reduce the risk of a fire starting within it.

LONGi’s Hi-MO X10 Guardian Fire-Resistant solar module incorporates these features alongside fire-resistant glass. The module passed TÜV Rheinland’s UL 790 Class A spread-of-flame and burning-brand tests. The burning source did not penetrate the module or roof covering, and the module did not sustain flaming. The test specimens were randomly selected from a normal production batch.

The Hi-MO X10 Guardian Fire-Resistant module also achieved Class B under EN 13501-1 for reaction to fire and passed testing for B ROOF (t4) under EN 13501-5 – the highest external roof-fire performance classification within the t4 method.

Visit the website for more information on the Hi-MO X10 Guardian Fire-Resistant solar module: https://eu.longi.com/solar-panels/fire-resistant