SEMCO Duct & Acoustical Products, Inc. offers six standard spiral duct and fitting gauge standards designated as SH95P, SM95P, SL95P, SH95N, SM95N and SL95N, all of which are designed to meet the latest SMACNA standards as published in their “HVAC Duct Construction Standards, Metal and Flexible, Second Edition - 1995”. Each of the listed standards is available with fitting and rolled duct seams welded or tack-welded and sealed. Oval duct and fittings will require external reinforcing on some sizes and for some pressures to maintain wall deflection within allowable limits as shown on page 6-10 in the product catalog.

Please refer to the Product Catalog for additional information. In addition to these gauge standards, other gauge and construction combinations are also available.

Leakage Class

According to SMACNA's HVAC Air Duct Leakage Test Manual (1st Ed., 1985), Section 4, "Leakage classification identifies a permissible leakage rate in cfm per 100 square feet of duct surface according to the relationship C_L = F / (P)^.65."

F is the leakage rate in cfm/100 s.f. of duct surface (It varies with static pressure).
P is the static pressure.
C_L is the leakage class and is a constant.

Leakage classifications are relative to duct type, seal classes, and construction pressure classes. Duct with a leakage lower or equal to that associated with the specified leakage class is considered in compliance.