When choosing ductwork for a fume hood exhaust system, the type of fumes likely to be produced must be taken into account.
Plastic ductwork presents a problem when the fumes to be extracted are acidic and/or solvent; in this circumstance, fire dampers are impractical and an alternative solution must be used. As a solution, plastic ductwork can be enclosed within a fire rated casing. The outer casing would resist fire from inside (Type B) and from outside (Type A), maintaining stability and integrity.
- Fire dampers should not be used where plastic ductwork is installed to resist acidic fumes and solvents.
- Alternative solutions must be found for crossing exit corridors and going from one compartment to another.
- Ductwork conveying polluted air must take into account the particular hazard involved and the likely contribution to fire spread.
In the diagram:
Duct, shown 
, is a plastic duct installed inside an outer fire rated casing
(duct within a duct).
Where the fume exhaust duct crosses the exit corridor, shown 
,
the duct would require stability, integrity, and insulation for the same
period of time as the compartment through which it passes. This may also be
required for the remainder of the ductwork route through the building to the
outside. Plastic ductwork can be used dependent on the application.
All FLAMEBAR BW11 Fire Rated Ductwork and Penetration Seals have been tested to ISO 6944 (1985) and manufactured and installed as tested or assessed by an International Accreditation Services Accredited Laboratory.
Note: Final approval must always be obtained from the Authority Having Jurisdiction prior to commencement of construction.
