As shown in Figure 4, ElL of the mixture of formaldehyde, PAN, PBzN and 03
indicated the steep inclination. Threshold value of eye irritation (represented with RDT)
was indicated in the con. of 0.14 ppm for the mixed gas. It has been revealed that in the
mixed gas the concentration can be obtained by making an arithmetrical summation of
those for each irritant, when they converted to formaldehyde's concentration. The same
results were represented in the relation RDT and ElL as shown in Figure 5. Until ElL
reaches "severe" level, it takes 62 seconds in case of formaldehyde, while in case of the
mixture gas the same fact occurred at 58 seconds. On the contrary, "barely noticeable"
level begins at 153 seconds in the latter case and then in the former case, 121 seconds.