Commercial Kitchen Hood Exhaust (IMC 507)

Type I (grease) and Type II (vapor-only) commercial-kitchen hood exhaust airflow per IMC 2021 §507.13 / §507.20 duty multipliers. Makeup air, duct area, grease-duct slope reminder. NFPA 96 governs grease-handling exhaust system design.

Type I: Q = duty_multiplier * L. Wall-canopy duty multipliers (light 200, medium 300, heavy 400, extra-heavy 550 cfm/ft) per IMC 2021 §507.13. Single-island canopy (400 / 500 / 600 / 700). Double-island (250 / 300 / 400 / 550). Backshelf / proximity / pass-over (250 / 300 / 400; extra-heavy not allowed). Type II: Q = 100 * L (IMC 507.20). Makeup = 0.80 * Q (IMC 508 balance check). Duct area (in^2) = Q / V * 144.

IMC 2021 §507.13 (Type I) and §507.20 (Type II). NFPA 96-2024 governs grease-handling exhaust system design.

codes.iccsafe.org for IMC TOC; nfpa.org/freeaccess for NFPA 96 TOC.

Estimate. AHJ and licensed mechanical contractor govern. ACCA Manual J / D / S supersede rules of thumb.

Field names used by the API: hood_class, hood_type, duty, length_ft, duct_velocity_fpm, Q_exhaust_cfm, cfm_per_ft, makeup_cfm

• Hood-type x duty matrix wall-canopy / single-island / double-island / backshelf / proximity / pass-over, each with light / medium / heavy / extra-heavy multipliersIMC 2021 §507.13
• Type II rate 100 cfm per linear foot for vapor-only hoodsIMC 2021 §507.20
• Makeup air 80% of exhaust as a balance-check rule of thumb; AHJ governs final balanceIMC 2021 §508
• Duct velocity range Type I grease-duct velocity 500-2000 fpm to keep grease suspendedNFPA 96-2024 §8.2.1.1
• Grease-duct slope 1/4 in per ft minimum slope back to the hoodIMC 2021 §506.3