Electronics (Soldering)

Where are the hazards?

Serious health problems may arise from inhalation of fume from rosin (sometimes called 'colophony') or its derivatives contained in solder fluxes.

Without effective control, solder fume rises vertically and, for manual operations, is likely to enter the breathing zone of the solderer. 

Rosin-based fluxes may be integral with the solder or applied separately, as in liquid fluxes. For solder wire, commonly used in hand soldering, the flux is often contained in a central core and is released on heating. In other cases, the flux may be within a solder paste applied by syringe, or by stencil and screen printing. Liquid fluxes may be applied from a bottle or by dipping into small jars or pots. On automated lines, the flux may be sprayed as a liquid or foam before wave soldering.

A large number of people, including telecommunications engineers, ventilation and heating specialists, plumbers and those in technical research and further education do some soldering. Intermittent soldering work may lead to high, short-term exposures, particularly if carried out in an enclosed space or at an awkward angle. People maintaining and cleaning soldering plant, equipment and control systems may also be at risk.

What are the risks?

Rosin-based solder flux fume is now regarded as one of the most significant causes of occupational asthma in Britain. When the asthmatic effects are fully developed they are permanent and irreversible. Continued exposure, even to very small amounts of fume, may cause asthma attacks and the person affected may be unable to do any soldering with rosin-based fluxes again.

How to control

As exposure to rosin-based solder flux fumes may be hazardous to health, their use is subject to the Control of Substances Hazardous to Health Regulations (COSHH) 2002 (as amended). A suitable assessment of the risks to health must be carried out. Where reasonably practicable, exposure should be prevented or, failing that, adequately controlled.

Things to consider:

  • Do you have to use flux containing rosin? There are other fluxing agents available
  • Never overheat the soldering iron
  • Use fume extraction
  • Keep your head out of the plume of solder fume

Is this page useful?

Updated: 2021-01-18