Solar module manufacturer LONGi is cautioning industry buyers that a "Class A" fire rating does not guarantee uniform safety performance across different photovoltaic (PV) products. While Class A is a standard industry benchmark, the company warns that the label can mask significant variations in how modules react to fire and contribute to its spread.
Understanding the Limitations of Class A
According to LONGi, the Class A designation—typically associated with the UL 790 standard—measures a module’s resistance to severe external fire exposure. However, it does not classify a module as "fireproof," nor does it indicate how close a specific product came to failing the test. Because different modules can pass the same test while exhibiting varying degrees of flame spread, the company argues that buyers should request detailed, measured test results rather than relying solely on a binary "pass" rating.
Furthermore, international standards differ in their focus. While UL 790 evaluates external fire resistance, European standards like EN 13501-1 assess a product’s contribution to fire development, and EN 13501-5 evaluates a roof’s response to external fire. A module that passes one test does not automatically satisfy the requirements of others.
A Two-Pronged Approach to Safety
LONGi emphasizes that true fire safety requires a dual strategy: preventing internal ignition and limiting external fire propagation. Internal risks, such as electrical faults and hot spots caused by shading, account for a significant portion of PV-related fire incidents. To mitigate these, the company suggests that modules should feature advanced cell-level current management and reinforced electrical connections to reduce the risk of DC arcing.
To address external threats, the company advocates for the use of high-strength, fire-resistant glass combined with flame-retardant materials within the module structure. These design features are intended to prevent flames from penetrating the module or the underlying roof covering.
While PV-related fires remain statistically rare—with European data suggesting an incidence rate between 0.006% and 0.014%—the potential impact on commercial and industrial rooftops remains high. By prioritizing both internal design integrity and external fire resistance, stakeholders can better protect critical infrastructure and inventory beneath solar installations.
