> How long would you suggest those tongs should be, to ensure a safe distance? For the ones that go bang.

I'm hesitant to answer in case some tries this and gets hurt.

I used a flexible claw (one like this: https://www.amazon.com/Flexible-Claw-Automotive-Mechanic-Gen...) inserted into a standard copper pipe (used for taps and other plumbing) to stiffen the spring and held it at arms length.

So, about 2m was safe for me. I also suggest wearing protection for your ears as these are really loud bangs, and protection for your eyes as well (it is an explosion, after all).

I think, given the HN community, the appropriate answer is "build a robot to do it for you"