Is Duct Tape Flammable? [The Fireproof Answer]

Although duct tape was originally designed to seal air ducts, it quickly became a popular DIY material due to its seemingly limitless versatility.

It’s used for everything from patching up broken car radiator hoses to removing pet hair.

The ease with which it can be used and its durability make duct tape a favorite among homeowners and contractors who are looking for a quick fix without spending a lot of money.

However, with its many uses, there are many questions that arise. One of the most common ones is whether or not duct tape is flammable.

The duct tape isn’t intended to be used for fireproof applications unless otherwise specified by the manufacturer. It typically doesn’t ignite fast but still has the potential to catch fire and cause flames to spread.

Manufacturers may use different materials and processes to achieve different flame retardant properties in their tapes.

So it is critical to check the safety data sheet (SDS) for the specific tape to see how well it will perform in a fire.

What is duct tape made of?

Duct tape is typically composed of three layers. The exposed top layer is made of polyethylene, which is a plastic that makes the tape strong and durable.

Underneath that are a fabric-based middle layer and a rubber-based glue at the bottom.

Although each component of duct tape has a different flammability rating, they are all flammable and will ignite under the right conditions.

Polyethylene has a low oxygen index (LOI), and it drips when burned, which contributes to the spread of fire.

Given the widespread use and high flammability of polyolefins (the parent material of polyethylene), it’s not surprising that duct tape has the propensity to burn.

The fabric-based material that forms the middle layer of duct tape is made up of materials like cotton and/or polyester. The cotton will burn rapidly, while polyester is difficult to ignite but will burn vigorously if exposed to a flame.

The third layer, which forms the duct tape’s bottom, is made of a rubber-based adhesive.

The adhesives are highly flammable materials since they are based on petroleum derivatives. All of these elements we mentioned combine to form highly combustible duct tape.

However, duct tape manufacturers are aware that their product is used in a variety of applications that require varying levels of flame resistance.

As a result, they’ve created a plethora of duct tape variants with varying degrees of flammability.

Thus, it is important to check the SDS for each specific type of duct tape before using it in an application that might be susceptible to fire.

The below video shows the duct tape being set on fire. As you can see, it catches fire relatively easily which is enough to cause a fire if the condition is right.

What regulations govern the flammability of duct tape?

Duct tapes are used in a variety of applications, some of which require more fire resistance than others.

Knowing the need for fire resistance manufacturers developed flame retardant duct tapes with different fire ratings.

If you intend to use duct tape as an airtight sealant in ducting systems, it must comply with ASTM E84 (Standard Test Method for Surface Burning Characteristics of Building Materials) or ANSI/UL 723 (Standard for Test for Surface Burning Characteristics of Building Materials).

Both ASTM E84 and ANSI/UL 723 will require a maximum flame spread index of 25 with a maximum smoke-developed value of 50.

The tape (or any duct insulation material) that meets the 25/50 criterion is categorized as a “limited-combustible” material but still not “non-combustible”.

NFPA 90A also refers to ASTM C411 (Standard Test Method for Hot-Surface Performance of High-Temperature Thermal Insulation), which states that at a minimum continuing service temperature of 250°F (121° C), all pipe and duct insulation must not flame, flare, smolder, or smoke.

How are duct tapes classified for flame retardance?

We have already mentioned that duct tape should be considered a flammable product unless otherwise specified by the manufacturer.

However, not all duct tape is created equal.

The below video should give you an idea of how duct tape vs fire retardant tape behaves under fire.

Duct tapes with UL 723 and ASTM E84 ratings have met specific criteria for flame spread and smoke development when tested under laboratory conditions.

Products that do not meet UL or ASTM requirements may still have some fire-retardant properties. However, without testing, it is difficult to ascertain the level of retardance.

Manufacturers may also classify their duct tapes with different terms like non-flammable, flame resistant, flame retardant, and fire-rated.

Although these terms look and sound similar, they have different meanings and implications for use.

Therefore, it is important to understand the difference between these terms and what they mean for your application.

Non-flammable: This means that the duct tape will not ignite even when exposed to a flame. The word “non-flammable” is also used interchangeably with the term “self-extinguishing”.

Flame resistant: This means that the duct tape will burn, but not spread flames once ignited. Once the flame source is removed, the tape will stop burning.

Flame retardant: This means that the duct tape will not ignite and will also slow the spread of flames once ignited.

Fire-rated: This means that the duct tape meets specific fire test criteria established by agencies like UL or ASTM.

The above terms are often used interchangeably by manufacturers, but they do not all mean the same thing and should be clarified for a complete understanding of the product’s capabilities.

How can you ensure that duct tape is not flammable?

When it comes to ensuring that the duct tape you are using is not flammable, your best bet is to check with the manufacturer.

All UL or ASTM-rated duct tapes are required to have a fire rating, so if you see a tape that does not explicitly state its flame retardance qualities, it is most likely not UL or ASTM rated.

If in doubt, ask the manufacturer or a trusted professional to help you select the right tape for your application.

You can also create your own fire test using a flame torch to have a rough idea of how the tape behaves in the presence of fire.

Never trust self-claimed “flammability ratings”. If you intend of using the product in an application where fire resistance is needed, make sure the product has passed a test from a third-party independent testing agency.

Remember, using non-rated duct tape for an application that requires a fire-rated material could potentially lead to disastrous consequences. So it is best to make sure of the fire resistance qualities before using it.