Development of a push-pull ventilation system to control solder fume

mHand soldering using rosin core solder wire is common in the electronics i ndustry and several studies have implicated the aerosol produced when rosin flux is heated in causing respiratory sensitisation. Control of solder fum e is generally achieved using local exhaust hoods, simple blowers with a fi lter or low-volume high-velocity (LVHV) ventilation systems. None of these provide an ideal control system and so a push-pull ventilation design was d eveloped as an alternative. Laboratory tests of the system's capture effici ency were carried out using nitrous oxide tracer gas. Capture efficiency wa s generally greater than 90% with the push airflow operating. However, with out the push airflow, capture efficiency decreased sharply with increasing distance from the exhaust hood (between 38 and 58% at 420 mm. from the fron t of the exhaust hood with the same exhaust airflow used by the push-pull s ystem). The push-pull system was found to be relatively insensitive to obst ructions placed in the path of the air flow or the influence of cross draug hts. The system was tested in five electronics factories and the effectiveness w as compared to their existing ventilation systems. Where only a small amoun t of soldering was carried out both the in-house and push-pull systems seem ed to provide adequate control of inhalation exposure to rosin-based solder flux fume measured as total resin acids. However, the push-pull system pro vided more consistent control than the existing ventilation systems when la rger quantities of solder were used. In these situations the mean personal exposure level was reduced to below the UK Maximum Exposure Limit (MEL) of 0.05 mg/m(3) 8-h time weighted average in most instances. The corresponding mean personal exposure level with the in-house systems in operation was ab out three to four times the long-term MEL. Interpretation of these data is complicated because of high background contribution to exposure from poorly controlled soldering operations elsewhere in the factories. However, this study suggests that the in-house systems were relatively inefficient. (C) 2 001 British Occupational Hygiene Society. Published by Elsevier Science Ltd . All rights reserved.