The reality of the situation is that mattresses don't require flame retardant chemicals be added. There is no state or federal mandate that dictates chemicals must be put in a mattress. Every mattress must pass a flame test however, and without a prescription, each bed will pass this test or it cannot be sold in the US.
How the mattress manufacturer chooses to pass this test will effect how toxic or non-toxic the end result will be. It is possible to create a bed with no added chemicals that passes this test. We know that there are some people who claim that it is impossible to pass this test without added chemicals; they are undoubtedly trying to sell you a prescription mattress. The only reason to buy a prescription mattress is because you are allergic to the non-toxic materials in natural fire barriers, like wool. That being said, there are still some pretty noxious materials that are allowed inside of mattresses. You can first consider the foams, and how many of them will off-gas, or the chemicals added to some batting materials in order to pass the flame test cheaply. Furthermore, it can be difficult to identify what a given manufacturer uses in their fire barriers. Here are some tips to finding a bed without harmful chemicals added:
Contact Manufacturer Directly
There are quite a few organic mattress manufacturers out there. These companies tend to be much more health and body oriented than their mainstream counterparts, and you can generally trust that they use carded wool to meet the flame test, or cotton with boric acid. You can contact the manufacturers directly to see if they have added silica to their wool to pass the test more easily (some people believe that the silica can be a respiratory risk).
Cotton and Boric Acid
Cotton and boric acid are frequently used as a fire barrier. This is thought by many to be the most acceptable chemical flame retardant; others argue that boric acid is the same as roach killer, and can be absorbed by your skin at night. This does not appear to be a real health risk. Though boric acid is not carcinogenic like some flame retardant chemicals, the thought of acid near your skin can bother some consumers. Most would be comfortable with this as an inexpensive alternative to organic wool fire barriers (though not chemical free like the wool, it is not going to create health problems).
Dacron and Rayon Fiber
Another commonly used fire barrier is a combination of Dacron and rayon fibers. Dacron is a plastic, and rayon is a plant fiber product. These will not have an odor, and are commonly accepted as a safe, low cost fire protection layer.
Beyond these safe options, a Consumer Product Safety Commission study has permitted the use of several controversial chemicals beyond the boric acid. Among the approved chemicals are antimony, silicon (think sand), fiberglass, decabromodiphenyl oxide, ammonium polyphosphate, melamine, and formaldehyde. The study performed by the CPSC asserts that these chemicals pose no significant safety risk to the consumer. Still many people take issue with this assessment. However, where one person draws the line may be different from another; for example, most polyurethane foams are treated with formaldehyde; so if you have memory foam of conventional innerspring bed, you have already been exposed to this on an everyday basis. This does not mean that you will get cancer. Most people never develop significant chemical sensitivities to these odors, and chemical treatments. To some the odor of a new mattress or new carpet is overwhelming, and to others its hardly noticeable. Additionally, your home is probably insulated with fiberglass, but it's understandable that people have concerns about inhalation of glass particles, and it's reasonable to avoid having that in your bed. Decabromodiphenyl Oxide (DBDPO) has been banned in Washington, and Maine, and is no longer present in several national mattress companies bedding lines, but it can legally be present in most states.
Antimony in the form of Sb2O3 is another mildly controversial chemical flame retardant, though it has been tested relatively extensively. In other forms antimony can be toxic much like arsenic, however in this form it is essentially inert. It has been shown in the most recent studies to have no impact on the development of fetuses during pregnancy, and though it can pass into a mother's breast milk, is not present at significant levels.
Though there are materials that in large to limited quantities will contribute to health risks, including the chemicals PBDE and DBDPO, Tris, PCB and Asbestos, Melamine, and Formaldehyde. These treatments are becoming more rare as the potential risks become known, and the most common fire protection layer is becoming the low cost blend of Dacron and Rayon fibers. Some manufactures are even using it as a comfort layer in the quilts of mattresses. It never hurts to ask what the manufacturer is using in their beds to pass the flame test, but don't expect anything that will harm your health; it's not impossible, but it is becoming increasingly less likely.