Solder fumes from soldering using rosin-cored solder may cause asthma. You should always try and prevent exposure to any substances that may cause asthma. If that is not reasonably practicable, control short and long term exposures to prevent asthma developing by installing LEV (local exhaust ventilation or fume extraction). If an individual develops occupational asthma, even very low levels of solder fumes in the air can trigger an attack.
When solder flux is heated above 183 Deg. C, (or higher for Lead Free) a complex mixture of resin acid particulates (smoke) and gases are generated - this is called ‘COLOPHONY’ and is produced from Hand Soldering, Solder Pots and Fountains, Wave Solder machines and Reflow Ovens
To fully understand the problem, we need to understand what makes up a typical rosin based solder fume. A typical solder fume is a mix of very small particles (smoke) and gases which can be explained as around 95% particulates (the physical smoke plume), and around 5% gases and vapours which can contain a cocktail of Acetones, Methyl Alcohol, Formaldehyde, Carbon Dioxide, Diterpine Acid, Carbon Monoxide and Isopropyl Alcohol. Note: Even ‘Synthetic’ and ‘No Clean’ fluxes can lead to serious lung irritation
Once inhaled, the lungs cannot easily remove particle sizes under 10 microns. If you knew a human hair is approximately 100 microns in diameter, consider this – the largest solder fume particle is around 10 microns in diameter and the smallest is around 0.3 microns (you can only see 30 microns with a naked eye).
Inhalation of hazardous fumes causes many symptoms that include headaches, runny eyes and nose, sore throat, respiratory problems, asthma, dermatitis and acne, nose bleeds and even some can be carcinogenic (causes cancers). Some of these symptoms can occur several hours after exposure when at home watching television, and are not associated with work. This is called a ‘late asthmatic reaction’ and is often blamed on an allergy to the pet cat or dog !
Inhalation of hazardous fumes do also result in the unseen problems of reduced productivity and absenteeism, re-recruiting and re-training costs, operator compensation claims/litigation – many cases are well documented.
Assessing exposure to Solder Fumes - Colophony (in the UK)
The UK has assigned occupational exposure limits for rosin based solder fumes as follows
A special method of sampling (MDHS 83) is used to measure the ’resin acids’ in the fume. The Max Exposure Limit is set at: 0.05 mg/m3 as an 8 hour TWA and 0.15mg/m3 over 15 mins.
Note: Older lapel sampling methods do not provide accurate results.
It was found recently by the HSE themselves that even a ‘moderate amount’ of soldering when not extracted caused exposures over 50 times greater than the 8-hour Workplace Exposure Limit of 0.05 mgm-3 and over 30 times greater than the 15-minute Short Term Exposure Limit of 0.15 mgm-3.