By what method do your matresses meet fire safety regulations?

Hi,
Im really impressed with your site, and especially with your transparency about your matresses and how they're made.
However, I've been unable to find out whether or not you use fire retardant chemicals in your manufacturing process, or whether your matresses meet fire safety regulations purely through the choice of materials used.
Id really appreciate it if you could clarify this. I gathered from a previous question (a couple of years back) that you were planning to look into questions around fire retardance, but ive been unable to tell what the results of your investigations were(!)
I have complex health problems as well as a spinal injury, and I need a more stable, supportive matress but have been advised to avoid fire retardant chemicals. If you can let me know whether you use these chemicals, or offer me any other advice, Id be very grateful. Im feeling a bit bewildered right now, just trying to balance the differing things i need from a matress!
Thanks very much.