How We Solved the Problem of Textile Filter Combustion in a Paint Shop: A Practical Guide Using Halogen-Free Flame Retardants

Photo: 夜 咔罗 / Unsplash

In paint shops and surface treatment facilities, fire risk is one of the most common operational threats. In this case, the customer faced repeated ignition of textile filters in the extraction system, even despite adhering to standard safety measures. The cause was not only high temperatures or sparks but also the accumulation of flammable deposits from paints and solvents. The solution required a combination of the correct choice of flame retardants, adjustments to the application technology, and optimization of filter maintenance. We will show how we proceeded step by step—from risk analysis to final implementation.

Problem: Combustion of textile filters in the paint shop and its causes

In paint shops, textile filters are used to capture excess paint and solvents from exhaust air. Their combustion is a frequent problem that threatens not only worker safety but also production continuity. In our case, repeated ignition of the filters occurred due to a combination of high exhaust air temperature (up to 80 °C), accumulation of flammable organic substances, and insufficient fire resistance of the filter material itself. Particularly critical was the fact that the filters contained synthetic fibers with a low melting point, which easily ignited upon contact with sparks or hot particles.

Analysis showed that standard filters are not designed for such an aggressive environment. Moreover, the accumulation of dust and paint particles accelerated combustion, acting as fuel. Operating conditions—high humidity, the presence of solvents, and inadequate ventilation—further exacerbated the situation. It was clear that the solution had to include both the modification of filter materials and the optimization of operational parameters.

Selecting a Suitable Flame Retardant: Halogen-Free Solution

When searching for a suitable flame retardant, we focused on halogen-free options, which are more environmentally friendly and safer for workers' health. Although halogenated flame retardants are effective, they can release toxic gases during combustion, which is unacceptable in the confined spaces of a paint shop. Halogen-free flame retardants, such as phosphorus-, nitrogen-, or inorganic hydroxide-based compounds, offer comparable effectiveness without these risks.

In our case, we selected a phosphorus-nitrogen system that operates through a dual mechanism: upon heating, it forms a protective layer on the material's surface, preventing oxygen access, and simultaneously releases non-flammable gases that dilute flammable combustion products. This type of flame retardant is compatible with polyester fibers, from which the filters were made, and does not affect their mechanical properties. An important criterion was also resistance to chemicals used in the paint shop.

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Practical Implementation: Filter Modification and Testing

The implementation process began with laboratory testing of the selected flame retardant. The filters were impregnated with a solution containing 15–20% of the active substance, with the concentration optimized to avoid compromising the material's breathability. After impregnation, drying at 120 °C ensured even distribution of the flame retardant within the textile structure. Subsequently, the filters underwent a series of tests, including flammability tests according to standardized methods and simulation of operating conditions.

A key step was verifying the effectiveness in real-world operation. The filters were installed in a paint shop and monitored for three months. During this period, no ignition occurred, even at elevated exhaust air temperatures. It was also important to monitor whether the filters became clogged or their filtration efficiency deteriorated. The results confirmed that the flame retardant did not affect the functionality of the filters while significantly increasing their fire resistance.

Recommendations for Paint Shop Operators

Based on our experience, we recommend that paint shop operators pay increased attention to the selection of filter materials and their regular maintenance. Textile filters should be made from fibers with higher temperature resistance, such as modified polyesters or glass fibers, and treated with halogen-free flame retardants. It is also important to ensure regular cleaning of the filters to prevent the accumulation of flammable substances.

Operating conditions should be optimized to ensure that the temperature of the exhaust air does not exceed 70 °C and that adequate ventilation is provided. When using solvents, it is necessary to comply with safety regulations and ensure that the concentration of flammable vapors remains below the lower explosive limit. Regular training of personnel in fire protection and equipment maintenance is also crucial for preventing similar incidents.

Photo: Shikhar Rastogi / Unsplash

Chemical Mechanisms of Halogen-Free Flame Retardants: How They Work in Practice

Halogen-free flame retardants act on multiple levels, with their effectiveness depending on a combination of physical and chemical processes. In the case of textile filters in paint shops, phosphorus-nitrogen systems are most commonly used, which release acidic compounds when heated. These catalyse the dehydration of the polymer, forming a protective layer of carbonaceous residue (char). This layer insulates the material from oxygen and prevents flame spread. Another mechanism is the endothermic decomposition of additives, which removes heat from the reaction zone and lowers the temperature below the ignition point.

In practice, liquid halogen-free systems based on organophosphates have proven particularly effective, as they can be easily applied by impregnation or spraying. At temperatures above 200 °C, they decompose to form phosphoric acid, which promotes carbonisation. It is important that the flame retardant is compatible with the filter material – for example, low-viscosity additives are recommended for polyester fabrics, as they do not clog pores and maintain breathability. A properly selected system can extend the time to ignition by up to 300 % without negatively affecting the mechanical properties of the filter.

Optimising the Application Process: Key Parameters for Successful Impregnation

Successful application of halogen-free flame retardants requires control of several critical parameters. The first step is pre-treatment of the textile – removing dirt, oils, and paint residues that could hinder the penetration of the additive. Typically, degreasing is carried out in an alkaline environment at 60–80 °C, followed by rinsing with demineralised water. This is followed by drying to a residual moisture content below 5 % to prevent dilution of the active substance.

The impregnation process itself is most commonly carried out by immersion or spraying. For immersion, the key factors are the solution concentration (typically 10–25 % active substance) and exposure time (30–120 seconds). After impregnation, excess liquid must be removed by rolling or centrifugation to prevent crust formation on the surface. Final drying takes place at a temperature of 120–150 °C for 10–30 minutes – this step is crucial for fixing the additive and achieving optimal fire-retardant properties. To verify the quality of impregnation, standard flammability tests are used, such as the vertical burning method according to applicable standards.

Long-term stability and maintenance of treated filters: Practical operational experience

Treated textile filters with halogen-free flame retardants require a specific maintenance approach to preserve their fire resistance throughout their service life. In paint shops, exposure to aggressive chemicals such as solvents or paint residues is a critical factor. These can gradually leach the additive from the textile, so regular flammability testing is recommended at intervals of 6–12 months. Operational experience shows that filters in environments with high solvent concentrations can lose up to 40 % of their flame retardant effectiveness within two years.

Maintenance includes regular cleaning of the filters, while it is essential to avoid aggressive alkaline or acidic cleaning agents that could disrupt the structure of the additive. The optimal approach is to use neutral detergents with a pH of 6–8 and a washing bath temperature of up to 40 °C. After cleaning, it is advisable to re-impregnate the filters with a diluted flame retardant solution (5–10 % concentration) to restore the protective layer. In practice, implementing a filter lifespan monitoring system has proven effective, where the maximum usage period is determined based on operating conditions (temperature, chemical exposure), and preventive replacement is planned accordingly.

Need a Custom Solution?

Every operation has its specific fire protection requirements. GCG Group supplies a broad portfolio of flame retardants, including halogen-free systems, and provides technical support for their correct application. Detailed safety data sheets (SDS) and technical specifications are available for each raw material. Contact us – or browse our catalog of over 1,300 products right away.