Standards for Duct Manufacturing
| SMACNA | IS | |||||||||
| Duct Sizes mm | Operation Pressure | Low Pressure | Medium Pressure | |||||||
| 250 Pascal | 500 Pascal | 1000 Pascal | ||||||||
| – | Gauge | Connector Type | Gauge | Connector Type | Gauge | Connector Type | Gauge | Connector Type | Gauge | Connector Type |
| 0-450 | 26 | C&S/TDF | 26 | TDF | 26 | TDF | 24 | C&S | 22 | TDF |
| 451-750 | 26 | C&S/TDF | 26 | TDF | 24 | TDF | 24 | C & Standing S/TDF | 20 | TDF |
| 751-900 | 26 | TDF | 24 | TDF | 22 | Slip on | 22 | C & Standing S/TDF | 20 | TDF |
| 901-1000 | 26 | TDF | 24 | TDF | 20 | Slip on TTF | 22 | C & Standing S/TDF | 20 | TDF |
| 1001-1200 | 24 | TDF | 22 | Slip on TTF | 18 | Slip on TTF | 22 | TDF | 20 | TDF |
| 1201-1300 | 24 | TDF | 20 | Slip on TTF | 18 | Slip on TTF | 22 | TDF | 18 | TDF/Slip on TTF |
| 1301-1500 | 24 | Slip on TTF | 18 | Slip on TTF | 22 | TDF/Slip on TTF | 18 | TDF/Slip on TTF | ||
| 1501-1800 | 22 | Slip on TTF | 18 | Slip on TTF | 20 | TDF/Slip on TTF | 18 | TDF/Slip on TTF | ||
| 1801-2100 | 18 | Slip on TTF | 18 | Slip on TTF | 20 | TDF/Slip on TTF | 18 | TDF/Slip on TTF | ||
| 2101-2200 | 18 | Slip on TTF | 18 | Slip on TTF | 20 | DF/Slip on TTF | 18 | TDF/Slip on TTF | ||
| 2201-2400 | 18 | Slip on TTF | 18 | Slip on TTF | 18 | Slip on TTF | 18 | Slip on TTF | ||
| 2401-2700 | 18 | Slip on TTF | 18 | Slip on TTF | 18 | Slip on TTF | ||||