IS 655:2018 is the Indian Standard (BIS) for mechanical ventilation and air conditioning of buildings. This standard specifies the material, construction, and installation requirements for metal air-handling ducts. HVAC and MEP engineers use it daily to determine standard duct sheet thicknesses based on duct dimensions, specify jointing types, and calculate support spacing to ensure structural integrity and prevent noise.
Provides guidelines for the design, installation, testing, and maintenance of mechanical ventilation and air conditioning systems in buildings.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Standard Duct Material | Galvanized Steel (IS 2777) | Galvanized Steel (ASTM A653 / EN 10346) | SMACNA / DW 144 / EN 1507/12237 |
| Minimum Galvanization Coating Mass | Typically Z275 (275 g/m² total) | G60 (183 g/m² total) for SMACNA, Z275 (275 g/m² total) for DW 144/EN | SMACNA / DW 144 / EN 10346 |
| Maximum Aspect Ratio (Rectangular Ducts) | 4:1 | Typically 4:1 | SMACNA / DW 144 / General practice derived from EN standards |
| Leakage Test Pressure for Medium Pressure Ducts | Design Pressure | Operating Pressure (for low), up to 1.5x Operating Pressure (for medium/high, max 1000 Pa) for SMACNA; 1.5x Operating Pressure (max 2000 Pa) for DW 144; Specific pressure to demonstrate compliance with leakage class (e.g., 200, 500, 1000 Pa) for EN standards | SMACNA / DW 144 / EN 1507/12237 |
| Minimum Sheet Thickness (Rectangular, 500x500mm, Medium Pressure ~500 Pa) | 0.8 mm | 24 Gauge (0.68 mm) for SMACNA; 0.7 mm for DW 144; ~0.7 mm (performance-based) for EN standards | IS 655:2018 Table 1 / SMACNA 5th Ed. Table 1-1 / DW 144 (2016) Table 1 |
| Joint Sealing Requirement for Medium Pressure | All longitudinal and transverse joints shall be sealed | All longitudinal and transverse joints shall be sealed (for specified leakage classes/pressure ranges) | SMACNA / DW 144 / EN 1507/12237 |
| Common Transverse Joint Types | Bolted angle flanges, Pittsburgh lock, S & drive | TDC/TDFC, Slip and drive, Snap lock (SMACNA); Proprietary flange systems, standing seam, S & drive (DW 144); Not explicitly prescriptive; performance-based design (EN standards) | IS 655:2018 Clause 7.2.1 / SMACNA / DW 144 / EN 1507/12237 |