Abstract For better understanding of air quality, ultrafine particles (UFPs) emitted from laser printers were evaluated as a function of toner coverage, printer type, potential submicrometer particle sources, and fuser units. Emission measurements were conducted using 11 printers with different fuser units from a variety of manufacturers. Particle concentrations with different fuser units and temperatures were monitored using a condensation particle counter (CPC) from the chamber. The relationship between the emission rate and the temperature of a fuser unit is very strong. The regression relationship satisfies a positive exponential-rise equation. However, only a weak positive exponential-rise relation was observed with the mixed data from four different fuser units. This is one piece of evidence that suggests that other factors play a role in laser printer fine particle/ultrafine particle emission.