Caustic paint removers, generally sodium hydroxide (also known as bleach or caustic soda), work by breaking the chemical bonds in paint, usually by hydrolyzing the chain bonds of the polymers that make up the paint. One of the worst offenders and potentially deadly chemicals in paint strippers is methylene chloride. Major home improvement stores have removed products containing the chemical from their shelves, but they are still available. Like soy-based gels, they work more slowly to remove paint and coatings than more toxic products.
However, these first two options, SoyGel and Citri-Strip, are the best (most effective) strippers on the list. Citri-Strip is an industrial paint and varnish remover. Like soy-based products, it is a gel formula. It's not caustic or corrosive, and most people could use it indoors.
People who are sensitive to chemicals should try a sample of all the options on this list. Why choose Citri-Strip instead of soy-based Safenol? Chemical strippers break down and help release old paint or varnish so you can easily remove them, without burning the surface or creating paint particles or dust. I had to cut the window frame of a house from the 60s to leave it in bare wood because the paint was very cracked and alligator. Citri-Strip and most other chemical paint removers only remove one coat of paint at a time (even if they're advertised differently, trust me here).
There are some tips and tricks for success, which I cover in my reference sheet for stripping paint, but for the most part it's not a difficult process. I have a question: I dug and repainted old juicers from the 60s (they are aluminum) and I was looking for something non-toxic in which I could completely immerse or submerge them and remove the original paint.