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NFPA-45 duct fire dampers

NFPA-45 duct fire dampers

NFPA-45 duct fire dampers

rcook (Mechanical) 11 Jun 07 16:20  
I am working with the NFPA 45 code (lab ventilation). Section 6.10.3 - no fire dampers in lab hood exhaust systems. Also in 6.10.3 is an exemption describing a 'subduct' system.

We are looking at this section because we are manifolding hoods into a common riser. The riser is running in a rated shaft. Does the riser need to be run in a separate (dedicated) shaft?

Sorry to start a new thread but rcook original thread was locked. Please ref. ANSI/AIHA-Z9.5-2003. stating that "fire dampers shall not be installed in exhaust system ductwork". This is the industrial hygiene Laboratory ventilation standard and all engineers doing lab design must consider this the lab ventilation design bible.

You should also check current IMC codes regarding manifolding of lab fume hoods. My understanding is you are allowed to manifold certain types of chemical fume hoods inside any zone. Each zone must have a riser all the way to the roof or mechanical room. If you combine fume hoods in a vertical riser you are required to sprinkle the riser--which is a cost and maintenance killer. Combining multiple zones into any vertical riser greatly increases your exposure and liability.

If you are reading ANSI/NFPA-45-2000 make sure you read the part about General Purpose Fume hoods and the fact they are not suitable for explosion or blast protection. What we engineers miss is solvents and reactive chemicals are used in virtually every fume hood and as such explosions/fires and splash are a constant threat to the users. The skinny is solvents and/or reactive chemicals cannot be used in general purpose fume hoods. To provide the required worker protection from explosion/blast protection you must provide explosion resistant designs and the most commonly missed protection is horizontal sashes must be provided on all fume hoods.

Do not allow your architects or Owners to buy vertical only sahes or Lab Control systems that only track vertical sash movement.

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