The Dangers of Flux Fumes in Electronics Assembly

Flux is an essential material in electronics assembly, helping to clean metal surfaces and ensure reliable solder joints. However, when flux is heated during soldering, it releases fumes that can pose serious health risks if not controlled properly. In busy electronics environments where soldering is carried out daily, flux fumes can build up quickly, affecting not only operators but also surrounding staff. Understanding the dangers of flux fumes and how to control them is critical for protecting workers, maintaining productivity and meeting regulatory requirements. 

What Are Flux Fumes? 

Flux fumes are airborne by-products released when flux is heated during soldering processes. The composition of these fumes depends on the type of flux used, but they commonly include rosin and resin acids, volatile organic compounds, aldehydes and other chemical irritants. 

Rosin-based fluxes are particularly common in electronics manufacturing and are known for producing fumes that can sensitise the respiratory system. Even low concentrations can cause irritation, and repeated exposure increases the risk of developing long-term respiratory conditions. 

Why Flux Fumes Are Hazardous? 

Flux fumes affect the body primarily through inhalation. When breathed in, the fine particles and gases irritate the airways and lungs. Short-term exposure often causes coughing, sore throats, burning eyes and headaches. While these symptoms may seem minor at first, they are warning signs that the body is reacting to airborne contaminants. 

Long-term exposure presents more serious risks. One of the most documented outcomes is occupational asthma, particularly among workers exposed to rosin-based flux fumes. Once sensitised, individuals may react to even very small amounts of fumes, making continued work in soldering environments difficult without strict controls. 

Some flux fumes also contain compounds that can affect concentration and cause fatigue, increasing the likelihood of errors or accidents during precision assembly tasks. 

Where Flux Fume Exposure Is Highest 

Flux fumes are most concentrated in areas where soldering takes place frequently or continuously. This includes hand soldering stations, wave soldering lines, reflow ovens, repair and rework benches, training rooms and prototype labs. In facilities with multiple soldering points, fumes can accumulate rapidly if not extracted effectively. 

Because flux fumes rise naturally with heat, they can spread across benches and into surrounding work areas. General room ventilation is rarely sufficient to control this type of airborne contamination, which is why local extraction at the source is essential. 

How Flux Fumes Spread in the Workplace 

Once released, flux fumes follow air currents and can remain suspended for long periods. In enclosed or poorly ventilated spaces, this leads to widespread exposure beyond the immediate soldering area. Workers who are not directly soldering may still inhale fumes, increasing overall health risks. 

This behaviour makes source capture critical. Extraction systems must be positioned close enough to the soldering point to capture fumes before they disperse into the wider environment. 

Health Effects of Flux Fume Exposure 

Short-term effects of exposure include respiratory irritation, eye discomfort, headaches and reduced concentration. These symptoms often appear gradually and may be dismissed as part of the working environment. 

Long-term exposure increases the risk of chronic respiratory conditions, particularly occupational asthma. In severe cases, workers may be forced to leave soldering roles altogether, resulting in skills shortages and increased recruitment costs for employers. 

Legal Responsibilities and Compliance 

Under the Control of Substances Hazardous to Health (COSHH) regulations, employers are required to assess risks from hazardous substances and implement appropriate control measures. Flux fumes fall under these regulations because of their potential to cause respiratory harm. 

Employers must ensure that exposure is either prevented or adequately controlled, typically through engineering controls such as local exhaust ventilation. Systems must be maintained and tested regularly to ensure they continue to perform effectively. 

Health and Safety Executive guidance on controlling airborne contaminants emphasises the importance of local extraction for soldering operations. Employers must also keep records of LEV testing and maintenance to demonstrate compliance. 

LEV Testing and Maintenance Requirements 

LEV systems must be thoroughly examined and tested at least every 14 months. This involves checking airflow rates, hood effectiveness, ducting condition and overall system performance. Poorly maintained systems can lose efficiency without obvious signs, increasing exposure risks. 

At Purex, we support compliance through professional LEV testing and maintenance services that help businesses meet legal requirements and maintain effective extraction. 

How to Control Flux Fumes Effectively 

The most effective way to control flux fumes is to capture them at the source. Local exhaust ventilation systems designed for electronics assembly draw fumes away from the soldering point before they reach the breathing zone. 

We provide a range of clean air systems designed specifically for electronics environments. These systems combine high-efficiency particulate filtration with activated carbon to remove both solid particles and gaseous contaminants. 

Choosing the Right Extraction System 

Different electronics environments require different extraction solutions. Bench-level soldering stations benefit from compact, flexible extraction units, while larger production areas may require multi-arm or centralised systems. 

Our clean air systems are designed to be scalable and adaptable, ensuring consistent performance across a variety of electronics assembly applications. Some of our recommendations include the:  

• FumeCube range 

• 2 Tip 

• 3 - 15 Tip 

• 200i HP 

• 800 range  

The Importance of Training and Good Practice 

Even the best extraction system requires correct use. Operators must be trained to position extraction arms correctly, recognise reduced airflow and report issues promptly. Regular training helps ensure systems are used effectively and consistently. 

Maintenance teams should also be familiar with filter replacement schedules and basic system checks to prevent performance degradation. 

Consequences of Poor Flux Fume Control 

Failing to control flux fumes can lead to increased sickness absence, reduced productivity, staff complaints and potential regulatory action. In severe cases, businesses may face enforcement notices or fines for non-compliance. Over time, poor air quality can also affect equipment reliability and overall workplace morale. 

How Purex Helps Create Safer Electronics Assembly Environments 

We design and supply clean air systems that are engineered to capture and filter flux fumes effectively. These systems are supported by professional services including LEV installation, LEV testing and ongoing maintenance. 

By combining reliable extraction technology with expert support, Purex helps businesses maintain safe air quality and comply with health and safety regulations. 

Get in Touch  

Flux fumes are an unavoidable by-product of electronics assembly, but exposure does not have to be inevitable. With the right extraction systems, proper maintenance and good working practices, businesses can significantly reduce risks to their workforce. Contact us today to enquire about our LEV systems and services.