Emission of ink aerosol from ink-jet recorders

As a follow-up of two patients found to be allergic to EKG*ink, a study was made, using spectrophotometric and light microscopic methods, of the factors influencing the emission of ink aerosol from ink-jet recorders used in electrocardiographs. Ink aerosol concentrations were only detectable by spectrophotometry under extreme conditions. However, the light microscopic method was sufficiently sensitive. At the slow paper speeds normally used (10-25 mm/sec) and under normal working conditions, the concentration of ink aerosol near the recorder was less than 0.1 microgram/m3; but aerosol emission increased exponentially with increasing ink pressure, i.e. increasing paper speed. At the highest paper speed studied (200 mm/sec), the aerosol concentration 36 cm from the ink nozzles was about 65 micrograms/m3. An increase in the distance from the ink nozzles to the chart paper resulted in a decrease in ink aerosol emissions. Aerosol dissipation was decreased by local exhaust ventilation of the ink-jet recorder. However, a protective shield designed to catch emitted ink aerosol only reduced the aerosol concentration at the measuring point at slow paper speeds. At higher paper speeds, the concentration increased. The average ink aerosol concentration near modern electrocardiographs is low, but some EKG operations may result in high peak concentrations. The formation of ink aerosol could be considerably reduced by changing the rheologic properties of the ink.