Environ. Sci. Technol. 2009, 43, 1015–1022
An Investigation into the Characteristics and Formation Mechanisms of Particles Originating from the Operation of Laser Printers L I D I A M O R A W S K A , * ,† C O N G R O N G H E , † GRAHAM JOHNSON,† ROHAN JAYARATNE,† T U N G A S A L T H A M M E R , †,‡ H A O W A N G , † E R I K U H D E , †,‡ T H O R B O S T R O M , † ROBIN MODINI,† GODWIN AYOKO,† PETER MCGARRY,† AND MICHAEL WENSING‡ International Laboratory for Air Quality and Health, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia, and Material Analysis & Indoor Chemistry, Fraunhofer Wilhelm-Klauditz-Institute (WKI), Bienroder Weg 54 E, 38108 Braunschweig, Germany
Received August 5, 2008. Revised manuscript received November 2, 2008. Accepted December 19, 2008.
While current research has demonstrated that the operation of some laser printers results in emission of high concentrations of ultrafine particles, fundamental gaps in knowledge in relation to the emissions still remain. In particular, there have been no answers provided to questions such as the following: (1) What is the composition of the particles? (2) What are their formation mechanisms? (3) Why are some printers high emitters, while others are low? Considering the widespread use of printers and human exposure to these particles, understanding the process of particle formation is of critical importance. This study, using state-of-the-art instrumental methods, has addressed these three points. We present experimental evidence that indicates that intense bursts of particles are associated with temperature fluctuations and suggest that the difference between high and low emitters lies in the speed and sophistication of the temperature control. We have also shown, for the first time, that the particles are volatile and are of secondary nature, being formed in the air from VOC originating from both the paper and hot toner. Some of the toner is initially deposited on the fuser roller, after which the organic compounds evaporate and then form particles, through one of two main reaction pathways: homogeneous nucleation or secondary particle formation involving ozone.
1. Introduction Recently, several studies have reported that laser printers can be significant sources of ultrafine particles (
