The list isn't that long, and it is the same for any stainless work.
Here are a few sources, there will be some repetition in these, but they are good.
https://nickelinstitute.org/~/media/Files/Technica...
https://www.nickelinstitute.org/~/Media/Files/Tech...
http://www.stainless-steel-world.net/pdf/11012.pdf...
http://www.nipera.org/~/media/Files/TechnicalLiter...

I'll tell you the most common failure that I have seen.
-SS parts being contaminated by dust/grinding sparks from CS work
-using tools (grinder/sander/wire brush/file) that has ever been used on CS
-purge gas not clean enough (need low dew point and oxygen, good gas and fresh hoses)
-surface contamination from poor solvents, paint markers, temp sticks, and other foreign materials
With DSS heat input and interpass temp are critical. You need to look at using ASTM A923 as part of the weld procedure qualification.
If this is a lean duplex then it is fairly easy, 2205 is a little harder but not bad, the superduplex grades are very demanding.

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P.E. Metallurgy, Plymouth Tube

EdStainless , Thank you so much ,great sources and tips

When welding stainless and duplex stainless steels hexavalent Chromium can become and issue. I am not an expert on OSHA and their requirements so I suggest you speak with someone who can direct your situation. However, I do have some experience and think you should be proactive in your protection for your welders and do your own sampling before OSHA gets involved.

In our shop the welders themselves saw the most hex chrome exposure. The inspectors and other operators outside of the booths were well under exposure limits. Due the the welders exposure we had to setup a free optional screening for any cleaning room employee. All of our welders had air helmets and suits providing fresh air for breathing and cooling. A cleaning area was provided for the welders to clean their equipment. Training was mandatory as cleanliness of their equipment and work area is a key factor in preventing exposure. We had to ban any open drinking containers from the area and had to be rigorous in enforcing the ban on smoking. It can be difficult to explain to old welders why they can't smoke in a welding booth.

Even with all of these guards in place and with none of our welders testing high hex chrome levels, because of the high levels showing up on the sampling, we had to redesign our welding tables to create better air movement to keep the fumes away from the welder. This can become problematic as you need enough air flow to remove the fumes but not so much that you start stripping the shielding gas off of the weld.

Do you need to meet any NACE hardness or ferrite content requirements? Achieving the ferrite in CD3MN using the 2209 weld filler can be problematic.

In our shop we found that venting the local of the welding was enough to keep Cr+6 levels low enough to avoid any restrictions. We have been spot testing for about 20 years.
The EU is trying to push exposure limits crazy low, not sure what the status of that is.

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P.E. Metallurgy, Plymouth Tube