Fireboard Chemicals: What You Need to Know Fireboard Chemicals: What You Need to Know

A fireboard is a type of wood that was treated for fire retardation. The substances used in treating wood differ in the way they react to fire. Some are effective in contolling heat release, flame spread and ignitability. Very high classifications for flammable products can be attained. There are many wood treatments available which may be placed in three general classifications:

  • Those impregnated into composite wood products while manufacturing
  • Those incorporated under pressure into particleboard, solid wood, plywood and hardboard usually post manufacture
  • The type applied as surface coatings or paint after construction


Most manufacturers will not divulge the chemical formula for their product but fire retardant chemicals have been known for a long time. The chemicals are usually based upon nitrogen, silica, phosphorus, boron and combinations of these. Examples are:

  • Ortho-phosphoric acid
  • Ammonium sulphate
  • Mono-ammonium phosphate
  • Melamine phosphate
  • Di-ammonium phosphate
  • Borax/boric oxide/disodium octoberate/boric acid

How Do They Work?

The chemicals work in many ways. Some of these are:

  • Promotes formation of char
  • Converts flammable gases to non flammable gases like carbon dioxide and water vapour
  • Induces a surface glaze barrier
  • Induces a surface foam barrier
  • Terminates free radicals in the gas formation phase

Health and Safety

Concerns are being raised about the toxicological and environmental effects of building materials. Adding fire retardant chemicals to wood can have an effect on the environment. All of the aforementioned chemicals are regarded as safe when used in accordance with the recommendations of the manufacturer. Direct contact, however, with the chemicals in their purest form may cause adverse effects like eye or skin irritation. Extra precautions should be taken with melamine formaldehyde and boric acid resins. Boric acid is known to be non-toxic and non-carcinogenic. It is suspected, however, to adversely affect male fertility. Formaldehyde causes irritation of the skin, eyes and respiratory tract and could cause tumour formation. Fire retardant formulas do not use pure formaldehyde or boric acid. Boric acid converts into a salt and is used like that. Formaldehyde is a component of resin so is totally bound and thus immobilised. Untreated wood, like pine gives off formaldehyde. Minute amounts of flame inhibiting chemicals may be given off by the wood. Fire retardant chemicals for wood should be handled safely by the experts.

Safe Use of Fire Retardant Wood

The chemicals in fire retardant wood are generally totally safe. Wood is normally treated at high pressures with the chemicals then dried again at higher temperatures which embeds the chemicals deep under the surface of the wood. The chemicals are not normally volatile and are not easily carried in the air.

Waste Management

Fire retardant wood needs to be disposed of at the end of its useful life. Compared with other materials used in construction, the calorific value of wood (the heat it contains and is set free while burning) may be used for producing energy. The chemicals in the wood will not prevent it from burning although the treated wood should be mixed with untreated wood.

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