Soundproofing; Is it a fire hazard?

Are soundproofing materials flammable? Is it dangerous to install them in your home or during construction?
In this article, I will be going over if soundproofing can be considered a fire hazard, the different materials you can use and how flammable they are, and much more.

So, without any further ado, let’s get started!

Is soundproofing a fire hazard?

Materials used in soundproofing, such as drywall, rockwool, mass loaded vinyl, fiberglass, and others, are generally non-flammable and are, therefore, not considered to be a fire hazard. In fact, rockwool and fiberglass are used as fire-blocking agents.

It’s worth noting, however, that even though drywall, mass loaded vinyl, and some other materials that are typically used for soundproofing aren’t really that flammable, they may catch on fire if subjected to higher temperatures for an extended period of time.

But more on this once I talk about each of them.

Now, I think it’s important to mention the difference between soundproofing and acoustic treatment, or sound absorption, since most people tend to confuse the two or use the two terms as interchangeable.

Soundproofing vs Acoustic Treatment

Soundproofing is the process of isolating or blocking the sound, not allowing it to enter or to leave a room. To do this you will need to use materials that are designed to not let sound through, like drywall.

Sound Absorption, on the other hand, relies on materials that are good at absorbing sound, such as acoustic panels, acoustic blankets, etc. to reduce the echo inside of a room.

Sound absorption, while not being great at soundproofing, may still help with it, which is why you might want to use it in conjunction with sound-blocking materials to achieve the best results.

The materials used for soundproofing are generally completely different from the ones used for acoustically treating a room, and like I previously mentioned, soundproofing materials tend to be non-flammable, and this is mostly because they are built into the house’s structure, like walls, and should help prevent a fire from spreading.

You can learn more about the differences between soundproofing and acoustic treatment here.

Materials used for soundproofing are generally non-flammable

One of the functions of insulation materials is to keep heat and sound in- or out of the house/room, but since they tend to be a part of the house’s structure, they also need to at least not be flammable and keep a fire from spreading.

Although this isn’t always the case since some of these materials can definitely catch on fire, some of them do a decent job at it, while some others are even considered fire-blocking.

Is Rockwool Flammable?

Rockwool is made from 100% non-combustible fire-resistant stone wool that can withstand temperatures above 1.000°C, which helps prevent the spread of fire in a building. Therefore, rockwool could be considered a flame-blocking material.

Rockwool is also used for acoustic treatment. In fact, I built my own acoustic panels from rockwool and they are absolutely fantastic, way better than the ones made out of foam that you can buy online.

Is Fiberglass Flammable?

Fiberglass is a material that is made out of glass spun into thin fibers and it can withstand temperatures of 530°C, or about 1000°F, without any issues. However, fiberglass comes with a paper and foil backing which could catch on fire, plus it will start to melt at 1090°C, or 2000°F.

Just like with rockwool, fiberglass can also be used for acoustic treatment and many people use it for making acoustic panels (although some of the glass particles can become airborne and make their way into our respiratory system, which could be a potential health risk).

As far as acoustic insulation, health benefits, and fire resistance goes, rockwool is overall better than fiberglass in every regard.

Is Spray Foam Flammable?

Spray foam can ignite and burn if exposed to a sufficient heat source and therefore is considered to be combustible and should be handled accordingly. In addition to being flammable, this kind of spray foam has chemical properties that produce smoke when ignited, which can render occupants of a house unconscious and even lead to temporary blindness.

Almost all spray foam insulation available for purchase contains, or should contain, flame retardant, because untreated foam is a fire accelerant.

Most of the foam insulation products coming to the market are either polyurethane or expanded polystyrene foam, both of which are manufactured from petroleum derivatives. Untreated and exposed to elevated temperatures or flame, these foam products will burn vigorously, producing high quantities of smoke, and spreading fire.

The benefit of spray foam, however, is how easy it is to use and how well it performs in terms of heat- and sound insulation, but it’s definitely not as good for preventing fires as something like rockwool which can withstand temperatures of over 1.000°C, similar to fiberglass which won’t burn as well.

You can check this video where spray foam, as well as other insulation materials, are set on fire and you’ll see how the spray foam seems just slightly burn… until it doesn’t.

Testing The Burn Ability Of Insulation In Wall

Is Drywall Flammable?

Typical drywall has a thickness of 0.5 inches and is made out of gypsum pressed between two sheets of thick paper which, of course, are flammable, but the gypsum is not and it also has water incorporated in its structure, which evaporates in the presence of fire which helps dissipate heat.

Type X designated gypsum boards come in 5/8” thickness and feature some special fire retardant additives which should resist fire penetration for at least an hour if the sheets are applied in a single layer to both sides of standard wood framing, and half-inch sheets applied in the same manner can resist fire for 45 minutes.

Drywall is one of the best ways to soundproof an already existing wall, since it’s quite affordable and can be installed on top of existing walls, ceilings, etc.

Is Mass Loaded Vinyl flammable?

Mass loaded vinyl is designed to withstand high temperatures and generally has a flame spread rating of 25, which means that it won’t burn easily and is not very likely to contribute fuel to a fire, but this doesn’t mean that it’s not flammable at all since if exposed to high enough temperatures, the plasticizers within it may ignite.

Are Materials used for acoustic treatment flammable?

Traditionally, when we think about acoustic treatment, what comes to mind? Foam panels, right?

Well, the reality is that any material that is dense, thick and soft can be used to absorb soundwaves, so you can use any number of them. For example, high-end acoustic panels, such as the ones you see in music studios, are generally made out of rockwool or fiberglass (and are even better than the ones made out of acoustic foam).

If you want to know if rockwool or fiberglass are flammable, scroll up a little since I already wrote the answer to those questions.

It’s worth noting that there are a bunch of different materials used for absorbing sound, such as acoustic curtains, acoustic blankets, etc., which are all flammable, so keep that in mind as well.

Is Acoustic foam Flammable?

There are different classes of foam and they each have a different flame spread rating;

Class A foam would be a ceramic-based material which does not burn and has a flame spread rating of 0-25, whereas a class C foam is generally made out of polyurethane and does easily burn but eventually extinguishes. Regular acoustic foam panels are made of polyurethane, meaning that they are quite flammable.

You could certainly purchase class-A foam panels, but these cost a fortune when compared to something like rockwool, which is even less flammable (actually, it literally can’t burn), so my recommendation would be to always use rockwool, be it for acoustic treatment or for wall insulation.

What about Egg cartons?

First of all, egg cartons are very flammable, but they are also not good at absorbing sound either, they only disperse it. You should never “soundproof” or “acoustically treat” your room with egg cartons since there are serious risks involved and they don’t contribute in any way acoustically.

Flame Spread index

The flame spread index is determined by the distance that a flame travels along a test substrate in a specific timeframe to determine its propensity to burn and how rapidly it can spread flames.

It’s divided into these 3 classes:

ClassFlame Spread Index
  1. Class A fire ratings indicate a flame spread rating between zero and 25. Materials that fall into Class A or Class 1 include; brick, gypsum wallboard, and fiber cement exterior materials. These materials do not burn well and are very unlikely to contribute fuel to a fire.
  2. With a Class B or Class 2 fire rating, the flame spread rating would fall between 26 and 75. This rating is typical for slower-burning whole wood materials, such as planks that are in the same form as they were when they were cut from the tree.
  3. A Class C or Class 3 fire rating has a flame spread rating between 76 and 200, which incorporates building materials like plywood, fiberboard, and hardboard siding panels, as well as any of the faster burning whole woods.

What is a good flame spread index?

The lower the Flame Spread index the better, since this means that the flame won’t travel and spread as rapidly. Class A materials, which have a rating of 0-25, do not burn well and are very unlikely to contribute fuel to a fire, which makes them the safest ones.


Most of the materials used to soundproof a home are at least fire retardant, and rockwool can even be considered fire-blocking.

If you’re doing some soundproofing of your own in an already built house or if you’re installing acoustic treatment, then try and go for rockwool or fiberglass since they are the best in terms of flammability and sound absorption.

Last Updated on May 11, 2022 by Facundo

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