The NFPA sets clear, legally binding standards for the cleanliness of commercial kitchen exhaust systems in NFPA 96. All establishments must meet NFPA standards to comply with fire and building codes.
NFPA 96 dictates the maximum thickness of grease accumulation permitted before the system is considered out of compliance. Grease deposits must not exceed 0.01 inches on hoods, 0.02 inches on removable filters, and 0.04-0.08 inches on ductwork based on type.
In addition to strict grease thickness limits, the standard also mandates regular cleaning intervals from quarterly to as frequent as daily, depending on cooking operations. Certified cleaning professionals use instruments to measure grease deposits and verify compliance.