Hi sleepless in colorado,
The majority of mattresses in the industry use non chemical inherently fire resistant materials to pass the fire regulations (either a “sock” that goes around the materials in the mattress or a fire retardant barrier that is part of the mattress cover) and generally don’t add fire retardant chemicals to the fire barrier or the foam itself. There is more general information about fire barriers in post #2 here and the two posts it links to at the end.
I’m not sure where you read this but a mattress will tend to soften and break down from the top layers down and innersprings are a support layer which means they are not normally the weakest link in a mattress. The problem is that the most common innerspring mattresses in the industry are made by the major brands that tend to use lower quality foams and materials above the innersprings which are the reason that so many of them soften and break down more rapidly but this has nothing to do with the innerspring itself.
Steel innersprings are a very durable component that can make a very good choice for the support core of a mattress if the mattress uses good quality and durable materials above the innerspring that meet the durability guidelines here. The innersprings in a mattress will usually outlast the comfort layers on top of them so it’s always important to know the quality of all the materials and components in any mattress … innerspring or otherwise … so you can confirm the mattress doesn’t have any lower quality materials or weak links in the comfort layers especially. Mattresses that use lower quality materials above any support core (latex, innersprings, polyfoam, or otherwise) will also have the same issues.
Dunlop and Talalay both come in a wide range of firmness levels so either one can be firmer than the other depending on its specific firmness but if both of them are the same ILD (and the ILD is measured in the same way which isn’t always the case) then Dunlop would tend to “feel” firmer because it has a higher compression modulus than Talalay (it gets firmer faster as you sink into it more deeply).
As you mentioned though there are no “standard” definitions or consensus of opinions for firmness ratings and different manufacturers can rate their mattresses very differently than others so a mattress that one manufacturer rates as being a specific firmness could be rated very differently by another manufacturer. Different people can also have very different perceptions of firmness and softness compared to others as well and a mattress that feels firm for one person can feel like “medium” for someone else or even “soft” for someone else (or vice versa) depending on their body type, sleeping style, physiology, their frame of reference based on what they are used to, and their individual sensitivity and perceptions. There are also different types of firmness and softness that different people may be sensitive to that can affect how they “rate” a mattress as well (see post #15 here) so different people can also have very different opinions on how two mattresses compare in terms of firmness. This is all relative and very subjective and is as much an art as a science.
For most people a relatively thin mattress using extra firm latex (either Talalay or Dunlop) would be firmer than they would be comfortable with but there will always be some exceptions and I have seen a “few” people say that even extra firm latex was softer than they expected.
Having said that … you are the only one that can feel what you feel on a mattress so the only way to know for certain whether any mattress is “firm enough” for you (regardless of whether it would be firm enough for someone else) and is a good match in terms of comfort, firmness, and PPP (Posture and alignment, Pressure relief, and your own Personal preferences) will be based on your own careful testing or if you can’t test a mattress in person before you purchase it then your own personal experience when you sleep on it.
Latex is the most resilient (springy) type of foam material and while it may not be as resilient as an innerspring … there are many people that are surprised by the resilience of latex (that some people call “pushback”). Having said that … the resilience of a material isn’t directly connected to its firmness … just to how “springy” it feels. The firmness of a material is related to how strongly it resists compression regardless of its resilience. A wooden floor for example has no resilience or “pushback” and yet it is very firm.
“Support” is often misunderstood because the goal of a “supportive” mattress is to keep the spine and joints in neutral alignment and this requires the type of contouring support that allows some parts of the body to sink in more (softer) and some parts of the body to sink in less (firmer) and this will vary on an individual basis based on body type and sleeping style. There is more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support/alignment” and “comfort/pressure relief” and “feel” and how they interact together.
While it’s not possible to be specific … in very general terms and based on “averages” … side sleepers tend to need a softer mattress because the body has more curves that need to be “filled in” to provide suitable support (such as the waist) and more “bony prominences” (such as the hips and shoulders) that need to sink in more to relieve pressure when you are on your side and generally need thicker and softer upper layers that can contour to the shape of the body more effectively and more deeply. Back sleepers have less curves that need to be filled in (such as the small of the back or lumbar spine) and less “pointy” pressure points and generally do best with a little bit firmer mattress that has either thinner or firmer comfort layers to reduce the risk of their pelvis sinking into the mattress too much which can put the spine out of alignment and cause lower back pain. Stomach sleepers have the flattest and least “curvy” sleeping profile of all and so they tend to need a firmer mattress yet with thinner and/or firmer comfort layers to reduce the risk of their pelvis sinking into the mattress too much and sleeping in a swayback position which can put considerable strain on the lower back and also lead to lower back pain. Stomach sleeping is the “riskiest” sleeping position in terms of back and neck strain (the head is turned sideways which can strain the neck). Putting a thin pillow under the pelvis/lower abdomen may also help prevent stomach sleepers from sleeping in a swayback position.
Again though … the only way to know for certain whether any mattress will keep you in good alignment and relieve pressure in all of your sleeping positions (and good alignment and pressure relief are the two most important functions of any mattress) will be based on your own careful testing or your own personal experience when you sleep on it. A mattress that would be “perfect” for some people may be unsuitable for someone else to sleep on even if they are in the same general weight/BMI range or seem to have a similar body type and sleeping style.
I’m not sure where you live but if you let me know your city or zip code I’d be happy to let you know about the better options or possibilities I’m aware of in your area.
If you are committed to latex and there are no manufacturers or retailers that you can test in person that are in reasonable driving distance then of course you would be limited to online sources. If this is the case then the tutorial includes a link to a list of the members here that sell mattresses online (in the optional online step) and many of them sell latex and latex hybrid mattresses that use different types and blends of latex that have a wide range of different designs, options, features, firmness levels, return and exchange policies, and prices that would be well worth considering.
When you can’t test a mattress in person then the most reliable source of guidance is always a more detailed phone conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using (fast or slow response, resilience, firmness etc) and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else.
Any good online retailer or manufacturer will generally suggest a mattress that they believe has the best chance of success based on the information you provide them when you talk to them on the phone because this is in both your own and their best interests but once again at the end of the day the only way to know for certain whether any specific mattress is a good match for you in terms of comfort, firmness, and PPP will be based on your own careful testing and/or your own personal experience so if you can’t test a specific mattress in person then the options you have available after a purchase to either exchange the mattress or individual layers or components or return the mattress for a refund (and any costs involved) would generally become a more important part of your personal value equation just in case a mattress your purchase doesn’t turn out as well as you hoped for.
Phoenix