Hi mgcalley,
Welcome to the Mattress Forum! … and I’m glad you found us.
I noticed that you registered with your email as your username which means that automated spambots will be able to harvest your email and add you to their spam lists. If you’d like I can remove the @ and the domain after it and change your username to just mgcalley (or any username you wish).
The only reliable way to to assess the “safety” of different materials in more general terms is based on lab tests and the certifications they have for harmful substances and VOC’s so that you have some assurance than the VOC’s are below the testing limits for the certification (see post #2 here for more information about some of the more reliable “safety” certifications). If the materials in a mattress or the mattress itself has a reliable “safety” certification then for most people they would certainly be “safe enough” … regardless of the name of the manufacturer on the label.
All the major brands (such as Sealy/Stearns & Foster, Simmons, and Serta) tend to use lower quality materials in their mattresses than most of their smaller competitors that will tend to soften or break down prematurely relative to the price you pay which is why I would generally suggest avoiding all of them completely (and the major retailers that focus on them) along with any mattress where you aren’t able to find out the type and quality/durability of the materials inside it (see the guidelines here along with post #3 here and post #12 here and post #404 here).
Having said that … Simmons, Sealy, and Serta are all CertiPUR certified so there would be no reason to believe that any of their mattresses would be “less safe” than any of the Sherwood mattresses.
While it may be more information than you are looking for … there is a lot more information in post #2 here and the more detailed posts and information it links to about safe, natural, organic, “chemical free”, and “green” mattresses and mattress materials that can help sort through some of the marketing information and terminology that you will encounter in the industry and can help you differentiate between them and answer “how safe is safe enough for me” that can help each person decide on the types of materials they are most comfortable having in their mattress or on the certifications that may be important to them. These types of issues are complex and are generally specific to each person and their individual sensitivities, circumstances, criteria, beliefs, and lifestyle choices.
I would be very cautious about brand shopping in general because you are buying a specific mattress not the brand and most manufacturers have access to the same or similar components and materials. Many manufacturers make a wide range of mattresses that can vary from lower quality and less durable materials to higher quality and more durable materials in a wide range of prices. The name of the manufacturer on the label or the price of the mattress won’t tell you anything about whether a specific mattress is suitable for you in terms of “comfort”, firmness, and PPP (Posture and alignment, Pressure relief, and your own Personal preferences) or whether there are any lower quality materials or weak links in the design that would affect the durability and useful life of the mattress. There is more about the risks of brand shopping in post #5 here and post #12 here.
The only way to compare the quality and durability of a mattress to another mattress is by finding out and comparing the type and quality of the materials inside them (see this article and the quality/durability guidelines that it links to).
There is also more about Sherwood Bedding and some general guidelines that can help you make the best possible choice in post #2 here and the posts it links to that I would make sure you read as well.
Phoenix