Correction ISO 4406 87 and 99

ISO 4406 1987 counted at 2 particle sizes, 5 and 15 micron. ISO 4406:1999 counts at 3 sizes, 4, 6 and 14 micron. Loosely speaking, the 5 and 15 micron are loosely equivalent to 6 and 14 micron. So you could just read the particle counts at 6 and 14 micron. I would be interested to know why you don't change to ISO 4406:1999?
I hope this helps,
Matt.

Most of the guidelines are the same for both. So if you have a 12/14 guideline for 4406-87 (>5,>15), then it applies to the -99 count at the >6,>14 ranges.

The actual numerical lookup table ranges were designed to support maximum compatibility between the two standards.

If that was the question... :-)