How I made a small smokeless (low smoke) firepit using two stainless steel stockpots I picked up at Walmart.
8 qt stockpot: https://www.walmart.com/ip/Mainstays-Stainless-Steel-8-Quart-Stock-Pot-with-Lid/37320201?selected=true
12 qt stockpot: https://www.walmart.com/ip/Mainstays-Stainless-Steel-12-Quart-Stockpot-with-Lid/37320202?selected=true
16 qt stockpot: https://www.walmart.com/ip/Mainstays-16-Qt-Stainless-Steel-Stock-Pot-with-Metal-Lid/37320203?selected=true
I used the 8 qt and 12 qt sizes, but you could use the same method using the 12 and 16 qt sizes.
Update - I've since purchased a Breeo firepit. It's much larger and of course better built than my DIY, but the smoke free performance is basically the same. So far, it's amazing! I may do a video review at some point. If you are looking to buy a Breeo, please use my referral link: http://rwrd.io/20r2thl?s for
$50 off when you spend $400 or more. For the referral, I earn $50 in Breeo credit. Thanks!