Code Reference
MechanicalIMC 2021

Section 506.1/Commercial Kitchen Hood Requirements

IMC 506 covers Type I and Type II commercial kitchen hood requirements including sizing, exhaust rates, and fire suppression integration.

What this section requires

Type I hoods are required over commercial cooking appliances that produce grease-laden vapors (fryers, grills, ranges, ovens, broilers). Type II hoods are required over appliances that produce heat, steam, or products of combustion but not grease (dishwashers, steam tables). Hoods must extend beyond the cooking appliances by specific dimensions, and exhaust rates must meet Table 507.2.1 based on hood type and cooking equipment category.

Why this section exists

Commercial cooking generates large quantities of grease, heat, and combustion products that must be captured and exhausted to prevent indoor air quality problems, grease accumulation on building surfaces, and fire hazards. Type I hoods include grease filters and fire suppression systems because grease-laden exhaust is a significant fire risk. The sizing and exhaust rate requirements ensure complete capture of cooking effluent.

What plan reviewers look for

Plan reviewers verify that every piece of commercial cooking equipment on the food service drawings has the correct hood type (I or II) shown on the mechanical drawings. They check hood dimensions (overhang beyond equipment), exhaust rates against Table 507.2.1, fire suppression system integration for Type I hoods, and makeup air provisions.

Common violations

Type II hood specified where Type I required
A hood over a grill or fryer is specified as Type II (no grease filters, no fire suppression) when the cooking equipment produces grease-laden vapors and requires a Type I hood.
Hood does not extend beyond equipment
The hood is the same size as the cooking equipment below it, without the required overhang (typically 6 inches beyond the equipment on accessible sides).
No makeup air for kitchen exhaust
The kitchen hood exhaust system operates at high volume but no dedicated makeup air system is shown. The resulting negative pressure makes doors difficult to open and pulls unconditioned air from adjacent spaces.
Compliance tip
Coordinate the food service equipment plan with the mechanical hood layout. Classify each piece of cooking equipment as Type I or Type II. Dimension hood overhangs on the mechanical plan. Show the exhaust rate and makeup air rate for the kitchen system. Include the fire suppression system on Type I hoods.

Related IMC requirements

Section 507.2.1 provides exhaust rate tables for kitchen hoods. Section 508 covers commercial kitchen makeup air requirements. Section 501 covers general exhaust system requirements. NFPA 96 covers the fire protection aspects of commercial cooking operations.

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