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Grease Duct & Integral Fire-Rated Chase

All pipe models are UL 1978 grease duct rated to their relative clearance to combustibles (single-wall, double-wall air or blanket insulated). Zero Clearance grease duct models Z3 & Z4 are additionally UL 2221 rated to zero clearance to combustibles and have an integral 2 hour fire rated enclosure, not requiring a separate fire rated shaft.  Alternatively, the Z3 can be used for other hourly rated integral shaft needs.  Just call to inquire.

ZClear™ is the most innovative factory-built kitchen grease duct in the industry. With a zero clearance rating, our integrated chase construction sets the standard for design.

Available in both stainless and aluminized steel exteriors, ZClear™ can be customized to your unique application requirements. ZClear™ is the clear choice for new restaurant construction or retrofitting future expansions or modifications.

Integral Chase

No longer will architects or contractors need to design and install a fire-rated chase to provide protection as required for welded steel or other grease duct designs. The ZClear system helps reduce floor space requirements (fig.1) and additional time and costs associated with constructing an on-site fire chase (fig.2). 

Setting the Standard

ZClear meets the following straight codes and standards:


Z3/ZCYesYes: 2 HrYes: 1 Hr
Z4/ZC+YesYes: 2 HrYes: 2 Hr

*ASTM E2336 is only code required for field applied grease duct enclosure(i.e. grease duct insulation wraps applied to field fabricated grease duct


Energy efficiency and overall performance are greatly improved with round grease duct designs due to less flow resistance. In addition, round systems are much easier to clean and reduce the opportunity for grease accumulation in the corners, like rectangular systems, increasing the risk  of fire. 


Almost no slope is required on horizontal runs of ZClear. Carbon steel duct systems require a 1/4” drop per 1 foot of ducting for proper contaminant drainage. Example: A 40ft. horizontal run of AMPCO’s Grease Duct would require 10 inch less headroom than a typical field fabricated system.

Design Services

The modular concept of factory-built grease duct provides for maximum design flexibility and ease of installation. Just ask for ZClear when utilizing your design services engineer for a complete system layout.  The AMPCO engineering staff provides design services for special product applications and for installations requiring complex routing or unusual manifold systems.

Grease Duct "Footprint" - 24" I.D. ZClear™ vs. 12" x 36" Fabricated Welded Steel

Z-Clear Fig 1 and 2

Comparison of wrapped, welded steel and ZClear™ after 2000ºF (simulated grease fire) for 30 minutes.

Z-Clear Comparison

To the Left: ZClear™ after 2000ºF  (simulated grease fire) for 30 minutes
To the Right: 12”x36” rectangular, 16 Ga., welded, carbon steel duct with generic “wrap” insulation – after 2000ºF (simulated grease fire) for 30 minutes.

The Clear Advantage

  • Better flow characteristics
  • Prefabricated/modular design
  • Superior safety and high temperature resistance
  • Stainless steel maintains strength at much higher temperatures than carbon steel
  • Cylindrical duct systems are far superior structurally compared to rectangular ducts
  • Limited Lifetime Warranty