Fire Rated Exhaust Duct

Would depend on application, ie. kitchen with appliances such as deep fryers, griddles, or just general cooking. Please provide more information or check the IMC (International Mechanical Code) section 505 if residential or 506-510 if commercial for general specifications.

Smoke extraction for deep frying & smoke in building on fire thru smoke extractors. Inspectors generally follow NFPA where Indian fire codes are unclear

Where are you installing these, what country, state, county?? All depends... where. If all else fails, consult the Local Code Inspector. All the Inspector's I've dealt with, usually felt kinda honored to have someone ask for advice and include them rather than having to argue what's right and to code You could even gain some Brownie Points with them!

Installation in India. Local codes on smoke extraction are inadequate hence designs when based on NFPA/more stringent are acceptable. Worst cases of smoke movement are deep frying, tandoor & smoke extraction when building on fire

thickness 1.5 mm as per Qatar Building code

Thanks Humayun. I generally use 1.6-2mm thick mild steel ducts. However I was looking for a code to support my design. Could you specify the relavent code & its connection with NFPA/equivalent. Thanks

NFPA 96 states exhaust ducts shall be constructed of and supported by carbon steel not less than 1.37 mm (0.054 in) (No. 16 MSG) in thickness or stainless steel not less than 1.09 mm (0.043 in) (No.18 MSG) in thickness.

However, there are also requirements for clearance to combustible materials. The duct should be 18in away from combustible material, 3 in away from limited combustible material along its entire length, or it must have an acceptable clearance reduction system. (E.g., insulation, sheet metal, air space.) The risk is that a grease fire in the ducts will cause neighbouring material to catch fire. If the duct penetrates vertical fire barriers, the duct also has to be enclosed in a continuous fire-rated enclosure from the first barrier to the exterior. 1hr for <4 stories, 2hr for >4 stories.

There is lots more in the standard. I highly recommend buying and reading it.

As for parking exhaust, typically you need to provide fire dampers at penetrations of firewalls. You can get dampers for fire and smoke together.

Many thanks H2G. Basement - Fans will be mounted on wall directly hence why provide dampers. Further, Indian code confirms exhaust for each basement shall be provided seperately hence no common shafts.

2mm thick mild steel ducts duly welded are used in India