What is the required clearance to combustibles for a Type 1 grease duct (black iron)?

Per the International Mechanical Code (IMC Section 506), a standard, uninsulated Type 1 commercial kitchen grease duct must maintain a strict minimum of 18 inches of clearance to any combustible materials (like wood framing or drywall).

['Per the International Mechanical Code (IMC Section 506), a standard, uninsulated Type 1 commercial kitchen grease duct must maintain a strict minimum of 18 inches of clearance to any combustible materials (like wood framing or drywall).', 'The Fix: This clearance can only be reduced if you wrap the duct in an ICC-ES listed field-applied multi-layer fire barrier blanket system (like 3M Fire Barrier or FireMaster wrap).']

Stop if

• Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

Steps

• Stop and verify the approved detail, manufacturer instructions, foreman direction, and project specs before touching it.
• Per the International Mechanical Code (IMC Section 506), a standard, uninsulated Type 1 commercial kitchen grease duct must maintain a strict minimum of 18 inches of clearance to any...

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