Borate Flame Retardants

Disodium octaborate tetrahydrate (DOT) a borate compound, is available as a white powder which dissolves easily in water. Applications of this aqueously dispersed compound will increase the flame resistance of wood if high enough concentrations of DOT remain present in the wood after it dries. Fire retardant treatments of this material can be applied by spraying, soaking, or injecting wood with pressure treatments. However, any DOT treatment intended as a fire or flame retardant, must be applied by a licensed professional. We don't sell disodium octaborate tetrahydrate for use as a flame retardant, but it's useful to know any DOT treatments applied as a flame retardant are the same borates we recommend as a defense against insects and mold. So, if you contract with a fire retardant specialist to treat your new home, no further DOT treatments will be necessary, if disodium octaborate tetrahydrate is the primary active ingredient in the fire retardant application.

Among the most commonly used flame retardant agents, borates are effective because they resist fire in two different ways. First, when heated, borates release non-flammable fumes in the form of water vapor. Second, borates melt at low temperatures, and modify the chemical reactions of cellulose materials as they reach combustion levels by producing glassy residues. These residues, known as char, form a barrier known to be effective against combustion.

Borates are nearly ubiquitous as compounds of Boron, a non-metallic element. At least 19 naturally occurring borates are found in rocks, soils, fresh water, ocean water and sea salt, where these minerals provide vital nutrition for plant growth. Two of these borates (borax and boric acid) are particularly well suited for use as flame retardant materials. That's because their flame retardant characteristics are complimentary, and because their low toxicity to humans and mammals qualifies them for use as flame retardants in materials common to millions of residential settings. Disodium octaborate tetrahydrate is less toxic than sodium chloride (table salt), and it has never been listed as a known carcinogen. In fact, DOT is commonly used as a fire retardant in the cotton batting used in furniture and mattresses, and in cellulose insulation.

Because disodium octaborate tetrahydrate (DOT) breaks down into borax and boric acid when dissolved in water, it provides a good delivery system for a water-based, flame retardant blend of borax and boric acid. Moreover, DOT provides an efficient means for dissolving borax, because DOT dissolves easily in water, while borax isn't so easily dissolved on its own.

Borax and Boric acid work very differently as fire retardants. Borax inhibits the spread of flames across a surface while contributing to glowing and smoldering material in contained areas. Conversely, Boric Acid exhibits little suppression of flame spread, but it will reduce combustion in glowing and smoldering materials. As might be expected, Borax and Boric acid work very well in combination, suppressing flame spread and reducing combustion in glowing and smoldering areas.

In addition to its use as a flame retardant, disodium octaborate tetrahydrate is also used as a wood preservative to protect it from insects and mold. Many log home owners apply DOT as a penetrating wood preservative, and some log homes are available from the manufacturer with borate treated logs. Borate treatments can be applied using water-based solutions of DOT in low pressure, pump garden sprayers. Although this material presents very low risks for toxicity to humans, anyone spraying DOT or any type of coating or preservative should always protect their health with a respirator, and wearing nitrile gloves is also recommended.

We don't supply disodium octaborate tetrahydrate for use as a fire retardant, because without professional application, it's efficacy can't be guaranteed. However, we do recommend its use as a defense against insects and mold on exterior and interior wood building materials. DOT will remain water soluble after it dries. So, in order to prevent it from being leached from exterior wood surfaces by water, it is necessary to over-coat it with an exterior wood finish or stain. This will seal in the DOT and provide water repellant characteristics to add another level of protection.

When fully dissolved in water, sodium octaborate tetrahydrate will appear as a clear, colorless, odorless, and non-staining solution. In places where it didn't soak completely into the wood before drying, you may see a pale salty film on the surface. This is easily removed with steel wool or fine sandpaper. For more information, please contact us by using the phone number at the top of this page, or stop in for a visit at one of the two addresses listed below.

More information about sodium octaborate tetrahydrate, borax, and boric acid can be found by using the search tools on these websites:

US Environmental Protection Agency - epa dot gov

United States Consumer Product Safety Commission cpsc dot gov