What fabrics are inherently flame retardant?

There is a bio-based fiber which is naturally fire retardant with limited oxygen index of 49%. The fiber is from the ocean and is called alginate fiber or seaweed fiber. 

The alginate fiber can be spinned to yarn with other natural fibers like cotton fiber. And then we make fabric with these yarns. When the fabric is lighted, it burns without smoke and smell. It's 100% healthy and skin friendly. 

And compared the cost of other natural fire resistant yarns like silk, alginate fiber is more cost effective. It's the best choice for making fire retardant sleepwear or undergarment for children and adults.