• Codes
  • Features

    Features Overview

    Go to features
    Reference

    Reference.

    A reliable and up-to-date source of codes.
    Research

    Research.

    Rapidly and efficiently calculate project parameters.
    Collaboration

    Collaboration.

    Get everyone on the same page and streamline code research.
    Workflows
    Architects General Contractor Building Official & Plans Examiner Inspectors Owner Subcontractors Code Consultants
  • Pricing
  • Login
  • Sign Up
Sign Up
Login
  • Code Library
  • Features
  • Pricing
  • About
  • Careers
  • Help
  • Contact
  • Terms
  • Privacy
Sign Up
Upgrade to Premium
Code calculators: Code Calculators automatically generates a detailed list of requirements.
REFERENCE
Amendment Styling
Industry-leading search
Suggested code sections
Code diagrams
RESEARCH
Code calculators
Filter by topic
Code compare
Code sheet exports
COLLABORATION
Team projects
Bookmarks
Comments
START 2 WEEK FREE TRIAL
Have an account? Sign in
// CODE SNIPPET

506.11 Clearance Reduction Methods

California Mechanical Code 2019 > 5 Exhaust Systems > 506.0 Product-Conveying Ducts > 506.11 Clearance Reduction Methods
JUMP TO FULL CODE CHAPTER
It shall be permitted to protect stored combustible material or combustible construction from ductwork in accordance with Table 506.11 and Section 506.11.1 through Section 506.11.6. In no case shall the clearance between the duct and the combustible surface be reduced below that allowed in Table 506.11. [NFPA 91:4.7.4, 4.7.4.1]

TABLE 506.11
REDUCTION OF DUCT CLEARANCE WITH SPECIFIED FORMS OF PROTECTION
[NFPA 91: TABLE 4.7.4]
FORM OF PROTECTION* MAXIMUM ALLOWABLE REDUCTION IN CLEARANCE (percent)
AS WALL PROTECTOR OR
VERTICAL SURFACE
AS CEILING PROTECTOR OR
HORIZONTAL SURFACE
31/2 inch thick masonry wall without ventilated air space 33 None
1/2 inch thick noncombustible insulation board over 1 inch glass fiber or mineral wool batts without ventilated air space 50 33
0.024 inch (24 gauge) sheet metal over 1 inch glass fiber or mineral wool batts reinforced with wire, or equivalent on rear face with at least a 1 inch air gap 66 66
31/2 inch (90 mm) thick masonry wall with at least a 1 inch air gap 66 None
0.024 inch (24 gauge) sheet metal with at least a 1 inch air gap 66 50
1/2 inch thick noncombustible insulation board with at least a 1 inch air gap 66 50
0.024 inch (24 gauge) sheet metal with ventilated air space over at least 0.024 inch (24 gauge) sheet metal with at least a 1 inch air gap 66 50
1 inch glass fiber or mineral wool batts sandwiched between two sheets of 0.024 inch (24 gauge) sheet metal with at least a 1 inch air gap 66 50
For SI units: 1 inch = 25.4 mm
* Clearance reduction applied to and covering all combustible surfaces within the distance specified as required clearance with no protection in Table 506.10.4.

506.11.1 Spacers and Ties

Spacers and ties for protection materials shall be of noncombustible material and shall not be installed on the duct side of the protection system. [NFPA 91:4.7.4.2]

506.11.2 Wool Batts Insulation

Mineral wool batts (blanket or board) shall have a density of not less than 8 pounds per cubic feet (lb/ft3) (128 kg/m3) and have a melting point of not less than 1500°F (816°C). [NFPA 91:4.7.4.3]

506.11.3 Insulation Board

Insulation board used as a part of a clearance-reduction system shall meet the following criteria:
  1. Have a thermal conductivity of 1 British thermal unit inch per hour square foot degree Fahrenheit [Btu•in/(h•ft2•°F)] [0.14 W/(m•K)] or less.
  2. Be formed of noncombustible material. [NFPA 91:4.7.4.4]

506.11.4 Duct and Thermal Shield

With all clearance reduction systems, not less than 1 inch (25.4 mm) clear space shall be provided between the duct and the thermal shield. [NFPA 91:4.7.4.5]

506.11.5 Thermal Shield and Combustible Surface

When using clearance reduction systems that include an air gap, not less than 1 inch (25.4 mm) clear space shall be provided between the thermal shield and the combustible surface. [NFPA 91:4.7.4.6]

506.11.6 Reduce Clearance With Air Gaps

When using clearance reduction systems that include an air gap between the combustible surface and the selected means of protection, air circulation shall be provided by one of the methods in accordance with Section 506.11.6.1 through Section 506.11.6.2. [NFPA 91:4.7.4.7]

506.11.6.1 Air Circulation

Air circulation shall be permitted to be provided by leaving all edges of the wall protecting system open with at least a 1 inch (25.4 mm) air gap. [NFPA 91:4.7.4.7.1]

506.11.6.2 Single Flat Wall

If the means for protection is mounted on a single flat wall away from corners, air circulation shall be permitted to be provided by one of the following:
  1. Leaving only the top and bottom edges open to circulation by maintaining the 1 inch (25.4 mm) air gap.
  2. Leaving the top and both side edges open to circulation by maintaining the 1 inch (25.4 mm) air gap. [NFPA 91:4.7.4.7.2]

506.11.6.3 Thermal Shielding

Thermal shielding that covers two walls in a corner shall be permitted to be open at the top and bottom edges with not less than 1 inch (25.4 mm) air gap. [NFPA 91:4.7.4.7.3]

Related Code Sections


506.11 Exhaust Systems, Clearance Reduction Methods
506.11. [NFPA 91:4.7.4, 4.7.4.1] TABLE 506.11 REDUCTION OF DUCT CLEARANCE WITH SPECIFIED FORMS OF PROTECTION [NFPA 91: TABLE ...
California Mechanical Code 2019 > 5 Exhaust Systems > 506.0 Product-Conveying Ducts > 506.11 Clearance Reduction Methods
506.11.5 Exhaust Systems, Thermal Shield and Combustible Surface
When using clearance reduction systems that include an air gap, not less than 1 inch (25.4 mm) clear space shall be provided between the thermal ...
California Mechanical Code 2019 > 5 Exhaust Systems > 506.0 Product-Conveying Ducts > 506.11 Clearance Reduction Methods > 506.11.5 Thermal Shield and Combustible Surface
506.11.6.1 Exhaust Systems, Air Circulation
Air circulation shall be permitted to be provided by leaving all edges of the wall protecting system open with at least a 1 inch (25.4 mm) air gap ...
California Mechanical Code 2019 > 5 Exhaust Systems > 506.0 Product-Conveying Ducts > 506.11 Clearance Reduction Methods > 506.11.6 Reduce Clearance With Air Gaps > 506.11.6.1 Air Circulation
506.11.6.2 Exhaust Systems, Single Flat Wall
If the means for protection is mounted on a single flat wall away from corners, air circulation shall be permitted to be provided by one ...
California Mechanical Code 2019 > 5 Exhaust Systems > 506.0 Product-Conveying Ducts > 506.11 Clearance Reduction Methods > 506.11.6 Reduce Clearance With Air Gaps > 506.11.6.2 Single Flat Wall
506.11.6.3 Exhaust Systems, Thermal Shielding
Thermal shielding that covers two walls in a corner shall be permitted to be open at the top and bottom edges with not less than 1 inch (25.4 mm) air ...
California Mechanical Code 2019 > 5 Exhaust Systems > 506.0 Product-Conveying Ducts > 506.11 Clearance Reduction Methods > 506.11.6 Reduce Clearance With Air Gaps > 506.11.6.3 Thermal Shielding
Help Contact Us Privacy Terms
Code diagrams
Code diagrams
Unpack the code through illustrations and descriptions.
Code Calculators
Code Calculators
Code calculators automatically generate a detailed list of requirements.
View thousands of relevant UL Certified products and assemblies that help achieve code compliance
View thousands of relevant UL Certified products and assemblies that help achieve code compliance
Access to UL product and system certification information.
Search
Search
Don't miss relevant code. Quickly locate sections across your jurisdiction.
Shared projects
Shared projects
Projects provide a dedicated space to collaborate on code research.
Code sheet exports
Code sheet exports
Generate a code sheet that integrates with your drawing set.
Code Compare
Code Compare
Highlight differences between any two building codes.
UpCodes Premium
Leverage the most sophisticated code compliance platform.
TRY FREE FOR TWO WEEKS VISIT PRICING
Join the waitlist
We are looking to gauge the level of interest in linking UL product and system certification information alongside related code sections.

Let us know your email and we’ll ping you once it’s ready! Learn more.

Thank you for your interest!

If you’re open to it, we would love to jump on the phone to make sure we’re building this in the best way possible for your workflow. Any insight or advice would be greatly appreciated. We’ve sent you an email with a calendar link to book at time with us.


Cancel
Get Early Access
UpCodes Premium
Leverage the full code compliance platform.
START 2 WEEK FREE TRIAL LEARN MORE