Hi Joenic,
Any manufacturer can use any materials that they choose in a mattress and most manufacturers make many different types of mattresses that use different materials so I would put much more focus on the materials inside a mattress than I would on the name of the manufacturer on the label. A mattress is only as good as its construction and the type and quality (and in your case “safety”) of the materials inside it. Focusing on the brand won’t tell you what you really need to know about a mattress (see post #2 here).
I also would be very cautious about using mattress reviews as a good source of information about a mattress since most consumers have very little knowledge about the materials inside the mattress they purchase and will often include information in their reviews that either isn’t accurate (or is just passing on what they’ve been told by someone that also knows little about mattress materials) or is only relevant or meaningful to them (see post #13 here).
Phoenix