Spray foam itself is combustible if directly exposed to flame. Building code requires a 'thermal barrier' (typically 1/2-inch drywall or DC315 paint) over foam in living spaces. Both code-compliant assemblies are standard practice on Cincinnati installs.
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Spray polyurethane foam combusts at 400-500°F if exposed to direct flame, releasing carbon monoxide and other toxic gases. Building code (IRC R316) requires a thermal barrier between foam and the occupied space to give fire response time and limit toxic-smoke generation. The standard thermal barrier is 1/2-inch gypsum drywall installed over the foam in living spaces. For attics and crawl spaces where drywall is impractical, code allows specific intumescent paint coatings (DC315 by International Fireproof Technology is the dominant Cincinnati-area product) sprayed over the foam at the manufacturer-specified thickness. Both options are code-compliant; the appropriate thermal barrier is specced as part of the project scope. Some product/assembly combinations have ignition-barrier provisions that may allow exemption from the full thermal barrier; code compliance is confirmed for the specific home and product as part of the scope. Cincinnati code-enforcement context: Cincinnati Building Department and Hamilton County Building Department both inspect foam installations for thermal-barrier compliance during permit-required projects. DC315 intumescent paint and 1/2-inch drywall are the two universally-accepted thermal barriers; alternative coatings exist but face more inspection variance. The appropriate barrier is specced in the project quote and applied as part of the original scope.