Fig. 3a and b shows the evolution of particle size distributions due
to the gas stovetop burner during the decay period (30 min) following
the peak concentration. The figures illustrate the temporal change
in UFP concentrations observed with the range hood turned off
(Fig. 3a) and on (Fig. 3b). During the decay, the total number concentration
decreases with time and the particle size distribution moves
toward larger particle size. This is caused mainly by coagulation in
which particles collide and stick together, resulting in formation of
larger particles. The coagulation loss is generally larger at higher
concentrations