The differences between spray and impregnated fire-retardant treatments

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Understanding the differences between spray and impregnated fire-retardant treatments for timber


Fire safety is a major concern in the timber industry, and as a result companies have turned to fire retardant treatments as a means of protecting timber structures from fire damage. However, with two main methods of fire-retardant treatment available – spray and impregnated – it’s important to understand the differences between them to select the most suitable treatment for a given application. Here, Bernie Roberts, our National Product Manager for Cladding Solutions, provides insights on the advantages and disadvantages of each method.


Q: What is a retardant spray?

A retardant spray, also known as a fire retardant spray, is a chemical product designed to provide temporary fire protection by reducing the flammability of various materials. It is typically applied to surfaces to create a fire-resistant barrier. The spray contains fire retardant chemicals that help slow down the spread of flames and inhibit combustion.

Retardant sprays are commonly used on a wide range of materials, including wood, fabric, paper, cardboard, and other combustible substances. They work by forming a protective coating or layer on the surface, which can resist ignition or delay the progress of fire. The specific formulation of retardant sprays may vary, but they often consist of fire-resistant substances such as ammonium phosphate, ammonium sulphate, borates, or other similar compounds.

Retardant sprays are usually applied using a pressurized spray can or pump sprayer. The spray is directed onto the surface to be protected, ensuring thorough coverage. Once applied, the retardant spray adheres to the material and provides a temporary fire retardant effect.

It’s important to note that retardant sprays typically offer temporary fire protection and may require reapplication over time. They are often used in environments where fire hazards are present or in situations where additional fire safety measures are needed, such as in residential homes, offices, theatres, or public venues. However, for long-term fire protection, other methods like fire-resistant construction materials or fire retardant treatments may be more suitable.

Q: What is impregnation fire retardant?

A: Impregnation fire retardant refers to a type of fire retardant treatment applied to materials to enhance their fire resistance properties. The term “impregnation” means to saturate or soak a material with a substance, in this case, a fire retardant.

Fire retardants are chemical substances that are designed to slow down or prevent the spread of fire. When materials are impregnated with fire retardants, it means that the fire retardant solution is applied to the material, allowing it to penetrate the surface and become integrated within the material’s structure. This impregnation process helps to provide long-lasting fire resistance.

Impregnation fire retardants can be applied to various materials, including textiles, wood, paper, and other porous or absorbent materials. The fire retardant treatment creates a protective barrier that can reduce the flammability of the treated material and delay its ignition or slow down the rate of combustion.

The specific composition of impregnation fire retardants can vary depending on the desired application and the material being treated. Common types of fire retardant chemicals used in impregnation treatments include halogenated compounds, phosphorous-based compounds, and intumescent agents.

It’s important to note that fire retardants do not make materials completely fireproof, but they can significantly improve their fire resistance properties. The effectiveness of impregnation fire retardants can depend on factors such as the concentration and distribution of the fire retardant within the material, as well as the specific conditions of the fire.

Q: What is the difference between flame retardant and fire retardant?

A: The terms “flame retardant” and “fire retardant” are often used interchangeably, but they can have slightly different meanings depending on the context. Here’s a general distinction between the two:

1. Flame Retardant: Flame retardants are substances or chemicals that are added to materials during manufacturing to inhibit or slow down the ignition and spread of flames. They work by either suppressing the chemical reactions that occur during combustion or creating a barrier that prevents the flame from reaching the underlying material. Flame retardants are commonly used in various consumer products such as furniture, electronics, and textiles.

2. Fire Retardant: Fire retardant is a broader term that encompasses both flame retardants and other fire safety measures. It refers to any substance, treatment, or strategy that helps prevent or reduce the intensity and spread of fires. Fire retardants can include flame retardant chemicals, as well as other measures like fire-resistant construction materials, fire suppression systems, and fire safety protocols.

In summary, flame retardants are specific chemicals or additives used to reduce flammability in materials, while fire retardant is a broader term that encompasses a range of measures aimed at fire prevention and control. Flame retardants are a subset of fire retardants, but the terms are often used interchangeably in general discussions.

Q: What are the differences between spray treatments and impregnated treatments for fire retardancy in timber?

A: Spray treatments involve applying a coating to the surface of the timber, while impregnated treatments involve forcing a fire-retardant solution into the timber.

Q: What’s the process of applying fire retardant treatments to timber using each method?

A: For spray treatments, a coating is applied to the surface of the timber using a spray gun or brush. For impregnated treatments, the timber is placed in a vacuum and the fire-retardant solution is forced into the timber fibre.

Q: What are two fire retardant treatments for timber?

A: There are various fire retardant treatments available for timber to improve its fire resistance. Two commonly used treatments are:

1. Pressure Impregnation: This treatment involves impregnating the timber with fire-retardant chemicals under high pressure. The timber is placed in a treatment vessel, and a fire retardant solution is forced into the wood cells using pressure. This process helps the chemicals penetrate deeply into the timber, providing long-lasting fire protection. Pressure impregnation treatments often utilize chemicals such as ammonium phosphate, borates, or ammonium sulphates.

2. Surface Coatings: Surface coatings involve applying fire retardant substances directly onto the surface of the timber. These coatings can be in the form of paints, varnishes, or sealants. The fire retardant chemicals in the coating create a protective layer that delays the ignition and spread of flames. Surface coatings are generally easier to apply and maintain compared to pressure impregnation treatments. However, they may provide less long-term protection and may require periodic reapplication.

It’s important to note that the effectiveness and specific fire resistance properties of these treatments may vary depending on the type of timber, the fire retardant chemicals used, and the application method. It’s recommended to consult with fire safety professionals or follow local fire safety regulations when considering fire retardant treatments for timber.

Q: What are the advantages and disadvantages of using spray treatments versus impregnated treatments?

A: While spray treatments may be quicker to apply, there is a risk of inadequate protection and the need for regular reapplication, plus it may alter the appearance of the timber. Meanwhile, impregnated treatments can be more expensive, however it provides peace of mind with longer-lasting protection.

Q: In your opinion, which method is more effective in providing fire protection for timber?

A: I firmly believe that impregnated treatments are more effective in providing fire protection for timber due, to their deeper penetration of the timber fibres and longer-lasting protection. Fire safety is not the place to take shortcuts, and therefore the specifications for spray treatment do not meet our own very high standards, particularly as it’s much harder to guarantee quality control. Our stance is also shared by industry-leading bodies such as the WPA.

Q: What do I need to know about regulations?

Spray applied products do still comply to the correct European standards. However, impregnated fire treatments are fully factory controlled and supported by independent tests. For example, our Burnblock impregnation treatment wood products are laboratory tested to BS EN 13501-1:2002; Fire classification of construction products and building elements. By comparison, it is difficult to apply quality control to site applied products – and you can never be too careful when it comes to fire safety.

Spray and impregnated fire-retardant treatments near me

At International Timber we offer a wide range of high-quality spray and impregnated fire-retardant treatments for your next project. Have any further questions? Contact our friendly experts today.

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