If a plenum duct liner has a smoke index of 49, is it compliant with the stated maximum?

If a plenum duct liner has a smoke index of 49, is it compliant with the stated maximum?

• A. Yes
• B. No
• C. Depends on other factors
• D. Not enough information

Answer: (A)

Materials used in plenum duct spaces must stay under a stated smoke index limit to keep smoke levels manageable in a fire. The smoke index shows how much smoke a material emits when it burns; lower numbers mean less smoke. Compliance means the material’s smoke index does not exceed the maximum allowed. Here, the liner’s smoke index is 49. If the stated maximum is 50 or higher, 49 is at or below that limit, so it meets the requirement and is compliant. The important idea is not the exact number by itself, but being at or under the cap set by the code. If the maximum were lower than 49, it wouldn’t comply; if higher, it would still comply.

Materials used in plenum duct spaces must stay under a stated smoke index limit to keep smoke levels manageable in a fire. The smoke index shows how much smoke a material emits when it burns; lower numbers mean less smoke. Compliance means the material’s smoke index does not exceed the maximum allowed.

Here, the liner’s smoke index is 49. If the stated maximum is 50 or higher, 49 is at or below that limit, so it meets the requirement and is compliant. The important idea is not the exact number by itself, but being at or under the cap set by the code. If the maximum were lower than 49, it wouldn’t comply; if higher, it would still comply.